If no image is generated, just return nil for the Openstack provider
If no image is generated, just return nil for the Openstack provider

This mirrors what is done in other providers e.g. Amazon providers

visioncritical/packer,sobrinho/packer,trumant/packer,vtolstov/packer,zeliff/packer,dantran/packer,rodm/packer,mansunkuo/packer,ephemeralsnow/packer,israelshirk/packer,justincampbell/packer,monkeylittleinc/packer,quantang/packer,ldejager/packer,c22/packer,hazelesque/packer,btd/packer,boumenot/packer,dev-head/packer,taliesins/packer,mefellows/packer,hashicorp/packer,rodm/packer,paulmey/packer,stagrlee/packer,marklap/packer,jsoriano/packer,pearkes/packer,visioncritical/packer,sgirones/packer,jarl-dk/packer,beni55/packer,sansb/packer,LinusU/packer,marc-ta/packer,vtolstov/packer,bradparks/packer__create_vm_for_aws_docker_vagrant_etc,tsmolka/packer,mitchellh/packer,DualSpark/packer,blairham/packer,markpeek/packer,arizvisa/packer,dayglojesus/packer,jen20/packer,mohae/packer,life360/packer,yonglehou/packer,threatstream/packer,danschaffer/packer,leroux/packer,pieter-lazzaro/packer,styro/packer,atlassian/packer,ober/packer,hasJackb/packer,tb3088/packer,yoctocloud/packer,rickard-von-essen/packer,paulvollmer/packer,bhcleek/packer,life360/packer,ricardclau/packer,sansb/packer,trumant/packer,threatstream/packer,youhong316/packer,youhong316/packer,pvandervelde/packer,c22/packer,shaunduncan/packer,ricardclau/packer,jean/packer,jen20/packer,arizvisa/packer,umang1912/packer,ober/packer,ephemeralsnow/packer,paulvollmer/packer,jsternberg/packer,mindjiver/packer,sobrinho/packer,jen20/packer,zhuzhih2017/packer,visioncritical/packer,hazelesque/packer,Xiol/packer,vtolstov/packer,ttaylor249/packer,pvanbuijtene/packer,feateds/packer,icnocop/packer,israelshirk/packer,tomwilkie/packer,mitchellh/packer,ricardclau/packer,marklap/packer,tb3088/packer,henrysher/packer,noplay/packer,KFishner/packer,jonathankarsh/packer,jsternberg/packer,markpeek/packer,p1-nico/packer,vtolstov/packer,threatstream/packer,mkuzmin/packer,hasJackb/packer,styro/packer,feateds/packer,youhong316/packer,tb3088/packer,hasJackb/packer,mindjiver/packer,smaato/packer,jarl-dk/packer,umang1912/packer,manicai/packer,cyberhouse/packer,monkeylittleinc/packer,bryson/packer,quantang/packer,sobrinho/packer,qur/packer,pvanbuijtene/packer,jimmythedog/packer,samdunne/packer,eranchetz/packer,markpeek/packer,burnzy/packer,jgkim/packer,jamesbishopp/packer,jszwedko/packer,jen20/packer,c22/packer,atlassian/packer,sgirones/packer,esemplare/packer,paulvollmer/packer,bryson/packer,dayglojesus/packer,masbog/packer,quantang/packer,markpeek/packer,qur/packer,rrva/packer,leroux/packer,masbog/packer,routelastresort/packer,ttaylor249/packer,mayflower/packer,jamesleech/packer,paulmey/packer,pieter-lazzaro/packer,mkuzmin/packer,gildas/packer-hyperv,p1-nico/packer,stagrlee/packer,styro/packer,jgkim/packer,trumant/packer,israelshirk/packer,dantran/packer,mkuzmin/packer,evertrue/packer,bryson/packer,ttaylor249/packer,ephemeralsnow/packer,rickard-von-essen/packer,oliviertremblay/packer,zeliff/packer,grubernaut/packer,routelastresort/packer,pecigonzalo/packer,pvanbuijtene/packer,mvanholsteijn/packer,mkuzmin/packer,sgirones/packer,mitchellh/packer,rnaveiras/packer,jonathankarsh/packer,routelastresort/packer,tb3088/packer,Sheile/packer,yoctocloud/packer,jean/packer,hazelesque/packer,napramirez/packer,dave2/packer,Akasurde/packer,dieu/packer,dev-head/packer,tsmolka/packer,DualSpark/packer,taliesins/packer,p1-nico/packer,p1-nico/packer,sean-/packer,avldya/packer,noplay/packer,jae2/packer,kgrvamsi/packer,jean/packer,tsmolka/packer,orivej/packer,burnzy/packer,Silver90/packer,Cbeck527/packer,BayanGroup/packer,jsoriano/packer,rickard-von-essen/packer,zeliff/packer,bensojona/packer,DualSpark/packer,lantrix/packer,mafrosis/packer,Akasurde/packer,tas50/packer,kgrvamsi/packer,aneeshusa/packer,dave2/packer,pearkes/packer,arizvisa/packer,tb3088/packer,jonathankarsh/packer,jsternberg/packer,icnocop/packer,gbarberi/packer,grange74/packer,arizvisa/packer,KohlsTechnology/packer,routelastresort/packer,mohae/packer,aneeshusa/packer,boumenot/packer,higebu/packer,dantran/packer,blairham/packer,mohae/packer,zeliff/packer,grubernaut/packer,markpeek/packer,jean/packer,ephemeralsnow/packer,atlassian/packer,grange74/packer,jimmythedog/packer,monsterzz/packer,aneeshusa/packer,fnoeding/packer,tracyde/packer,sansb/packer,mitchellh/packer,ChrisLundquist/packer,cyberhouse/packer,mayflower/packer,sean-/packer,arizvisa/packer,kpettijohn/packer,KFishner/packer,atlassian/packer,tas50/packer,mitchellh/packer,higebu/packer,eranchetz/packer,quantang/packer,mvanholsteijn/packer,justincampbell/packer,avldya/packer,marc-ta/packer,jszwedko/packer,KFishner/packer,evertrue/packer,tas50/packer,zhuzhih2017/packer,noplay/packer,ober/packer,jmptrader/packer,Silver90/packer,Xiol/packer,sneal/packer,tomwilkie/packer,Banno/packer,arizvisa/packer,timsutton/packer,rk295/packer,KohlsTechnology/packer,threatstream/packer,yoctocloud/packer,zakuro9715/packer,gildas/packer-hyperv,jszwedko/packer,bhcleek/packer,pvandervelde/packer,KohlsTechnology/packer,mohae/packer,sneal/packer,timsutton/packer,legal90/packer,mefellows/packer,c22/packer,grange74/packer,samdunne/packer,ttaylor249/packer,danschaffer/packer,jgkim/packer,jmptrader/packer,jae2/packer,bradparks/packer__create_vm_for_aws_docker_vagrant_etc,qur/packer,monkeylittleinc/packer,dayglojesus/packer,jmptrader/packer,ChrisLundquist/packer,bensojona/packer,KohlsTechnology/packer,jasonchaffee/packer,c22/packer,life360/packer,pecigonzalo/packer,LinusU/packer,dayglojesus/packer,sequenceiq/packer,leroux/packer,dragon788/packer,sean-/packer,kpettijohn/packer,pvanbuijtene/packer,pearkes/packer,eranchetz/packer,sgirones/packer,henrysher/packer,hashicorp/packer,aneeshusa/packer,rodm/packer,smaato/packer,samdunne/packer,youhong316/packer,ldejager/packer,evertrue/packer,blairham/packer,Sheile/packer,ttaylor249/packer,boumenot/packer,ricardclau/packer,dantran/packer,jasonchaffee/packer,avldya/packer,fnoeding/packer,LinusU/packer,noplay/packer,sean-/packer,grubernaut/packer,jamesbishopp/packer,pieter-lazzaro/packer,trumant/packer,beni55/packer,monkeylittleinc/packer,legal90/packer,rrva/packer,mohae/packer,routelastresort/packer,taliesins/packer,dieu/packer,mgk/packer,justincampbell/packer,mindjiver/packer,ChrisLundquist/packer,Cbeck527/packer,threatstream/packer,tas50/packer,dieu/packer,jonathankarsh/packer,mansunkuo/packer,dave2/packer,pvandervelde/packer,BayanGroup/packer,fnoeding/packer,smaato/packer,bryson/packer,marklap/packer,ricardclau/packer,grange74/packer,atlassian/packer,styro/packer,gbarberi/packer,jae2/packer,mgk/packer,c22/packer,zakuro9715/packer,mkuzmin/packer,jae2/packer,oliviertremblay/packer,sansb/packer,feateds/packer,orivej/packer,beni55/packer,bhcleek/packer,Silver90/packer,yoctocloud/packer,mindjiver/packer,hazelesque/packer,ldejager/packer,btd/packer,icnocop/packer,sobrinho/packer,boumenot/packer,lantrix/packer,mayflower/packer,umang1912/packer,jsternberg/packer,tracyde/packer,btd/packer,rk295/packer,bradparks/packer__create_vm_for_aws_docker_vagrant_etc,danschaffer/packer,rickard-von-essen/packer,bensojona/packer,mwhooker/packer,marklap/packer,mefellows/packer,gbarberi/packer,markpeek/packer,rk295/packer,youhong316/packer,mwhooker/packer,dayglojesus/packer,rickard-von-essen/packer,stagrlee/packer,avldya/packer,taliesins/packer,tb3088/packer,smaato/packer,jamesleech/packer,smaato/packer,yonglehou/packer,BayanGroup/packer,AlphaStaxLLC/packer,bradparks/packer__create_vm_for_aws_docker_vagrant_etc,monkeylittleinc/packer,bhcleek/packer,smaato/packer,dev-head/packer,orivej/packer,mwhooker/packer,ephemeralsnow/packer,monsterzz/packer,ober/packer,shaunduncan/packer,dragon788/packer,cyberhouse/packer,dev-head/packer,Akasurde/packer,kpettijohn/packer,dieu/packer,napramirez/packer,BayanGroup/packer,visioncritical/packer,tsmolka/packer,Akasurde/packer,manicai/packer,timsutton/packer,p1-nico/packer,lantrix/packer,blairham/packer,sequenceiq/packer,AlphaStaxLLC/packer,esemplare/packer,mayflower/packer,mayflower/packer,dave2/packer,Akasurde/packer,AlphaStaxLLC/packer,btd/packer,jimmythedog/packer,hashicorp/packer,zhuzhih2017/packer,legal90/packer,stagrlee/packer,higebu/packer,zhuzhih2017/packer,tas50/packer,paulmey/packer,jamesbishopp/packer,rnaveiras/packer,ldejager/packer,monsterzz/packer,yonglehou/packer,napramirez/packer,bryson/packer,rnaveiras/packer,KohlsTechnology/packer,yoctocloud/packer,sequenceiq/packer,quantang/packer,mkuzmin/packer,rnaveiras/packer,tas50/packer,Cbeck527/packer,paulmey/packer,esemplare/packer,manicai/packer,hashicorp/packer,kpettijohn/packer,orivej/packer,ober/packer,timsutton/packer,bhcleek/packer,DualSpark/packer,uber/packer,KFishner/packer,marc-ta/packer,sneal/packer,evertrue/packer,kgrvamsi/packer,henrysher/packer,jen20/packer,marc-ta/packer,tomwilkie/packer,rk295/packer,jmptrader/packer,mansunkuo/packer,life360/packer,mafrosis/packer,justincampbell/packer,mafrosis/packer,pieter-lazzaro/packer,timsutton/packer,pieter-lazzaro/packer,rnaveiras/packer,mgk/packer,legal90/packer,tomwilkie/packer,eranchetz/packer,gildas/packer-hyperv,burnzy/packer,rrva/packer,Banno/packer,pieter-lazzaro/packer,lantrix/packer,gbarberi/packer,pecigonzalo/packer,taliesins/packer,Sheile/packer,danschaffer/packer,pvandervelde/packer,taliesins/packer,oliviertremblay/packer,pvandervelde/packer,jamesleech/packer,fnoeding/packer,dave2/packer,mgk/packer,zakuro9715/packer,zakuro9715/packer,mansunkuo/packer,grange74/packer,oliviertremblay/packer,ricardclau/packer,zhuzhih2017/packer,shaunduncan/packer,tracyde/packer,jasonchaffee/packer,danschaffer/packer,samdunne/packer,pvandervelde/packer,higebu/packer,sean-/packer,mvanholsteijn/packer,sequenceiq/packer,jarl-dk/packer,henrysher/packer,dragon788/packer,timsutton/packer,uber/packer,jimmythedog/packer,cyberhouse/packer,Silver90/packer,Xiol/packer,grubernaut/packer,pearkes/packer,beni55/packer,paulmey/packer,mwhooker/packer,israelshirk/packer,leroux/packer,jamesbishopp/packer,qur/packer,manicai/packer,rodm/packer,Xiol/packer,icnocop/packer,life360/packer,Sheile/packer,zhuzhih2017/packer,jamesleech/packer,yonglehou/packer,jarl-dk/packer,napramirez/packer,masbog/packer,esemplare/packer,tsmolka/packer,mvanholsteijn/packer,jasonchaffee/packer,dave2/packer,hasJackb/packer,boumenot/packer,gildas/packer-hyperv,vtolstov/packer,rrva/packer,ChrisLundquist/packer,mefellows/packer,paulmey/packer,mwhooker/packer,mafrosis/packer,masbog/packer,jasonchaffee/packer,dantran/packer,icnocop/packer,Banno/packer,shaunduncan/packer,jsoriano/packer,rnaveiras/packer,paulvollmer/packer,esemplare/packer,jsoriano/packer,legal90/packer,mafrosis/packer,atlassian/packer,uber/packer,jgkim/packer,Cbeck527/packer,samdunne/packer,mansunkuo/packer,pecigonzalo/packer,uber/packer,jszwedko/packer,grubernaut/packer,AlphaStaxLLC/packer,feateds/packer,Cbeck527/packer,KohlsTechnology/packer,jimmythedog/packer,pvanbuijtene/packer,sneal/packer,bryson/packer,ChrisLundquist/packer,bensojona/packer,kgrvamsi/packer,monsterzz/packer,tracyde/packer,p1-nico/packer,sneal/packer,dragon788/packer,burnzy/packer,grubernaut/packer,LinusU/packer,sean-/packer,higebu/packer,ChrisLundquist/packer,jen20/packer,tsmolka/packer,umang1912/packer,youhong316/packer