Fix API samples generation.
Fix API samples generation.

In Change: Ie46b24a65145c407d46974b63a97a84911223547 a check
was added to _verify_response() to verify the samples.

However, when trying to generate new samples this blocks
_write_sample() because it attempts to read a non-existent file.

This change ensures that the sample is created before the
verification and still retains the behavior that the samples are
only updated on changes.

Change-Id: I1527ba71676b2e1e10bd334f2a7878404d12600c

BeyondTheClouds/nova,shootstar/novatest,berrange/nova,gspilio/nova,varunarya10/nova_test_latest,bclau/nova,sacharya/nova,fajoy/nova,DirectXMan12/nova-hacking,orbitfp7/nova,maheshp/novatest,maelnor/nova,bgxavier/nova,openstack/nova,Juniper/nova,eayunstack/nova,houshengbo/nova_vmware_compute_driver,jianghuaw/nova,gooddata/openstack-nova,cloudbase/nova,maoy/zknova,CEG-FYP-OpenStack/scheduler,tanglei528/nova,devendermishrajio/nova_test_latest,mahak/nova,dawnpower/nova,leilihh/novaha,zaina/nova,sridevikoushik31/openstack,OpenAcademy-OpenStack/nova-scheduler,houshengbo/nova_vmware_compute_driver,watonyweng/nova,rajalokan/nova,cloudbau/nova,sacharya/nova,fnordahl/nova,NeCTAR-RC/nova,maoy/zknova,eharney/nova,sridevikoushik31/openstack,takeshineshiro/nova,DirectXMan12/nova-hacking,blueboxgroup/nova,cloudbase/nova,luogangyi/bcec-nova,openstack/nova,joker946/nova,yatinkumbhare/openstack-nova,jianghuaw/nova,rajalokan/nova,Brocade-OpenSource/OpenStack-DNRM-Nova,jianghuaw/nova,phenoxim/nova,Francis-Liu/animated-broccoli,whitepages/nova,citrix-openstack-build/nova,imsplitbit/nova,Triv90/Nova,ewindisch/nova,gooddata/openstack-nova,joker946/nova,whitepages/nova,devoid/nova,saleemjaveds/https-github.com-openstack-nova,rrader/nova-docker-plugin,virtualopensystems/nova,alexandrucoman/vbox-nova-driver,yosshy/nova,cernops/nova,JioCloud/nova,isyippee/nova,Juniper/nova,Tehsmash/nova,viggates/nova,fajoy/nova,sebrandon1/nova,tianweizhang/nova,maheshp/novatest,alaski/nova,barnsnake351/nova,TieWei/nova,kimjaejoong/nova,Brocade-OpenSource/OpenStack-DNRM-Nova,ntt-sic/nova,spring-week-topos/nova-week,leilihh/novaha,silenceli/nova,maoy/zknova,qwefi/nova,CCI-MOC/nova,cloudbase/nova-virtualbox,petrutlucian94/nova_dev,dstroppa/openstack-smartos-nova-grizzly,scripnichenko/nova,SUSE-Cloud/nova,klmitch/nova,badock/nova,rahulunair/nova,jeffrey4l/nova,klmitch/nova,apporc/nova,affo/nova,houshengbo/nova_vmware_compute_driver,vmturbo/nova,nikesh-mahalka/nova,bgxavier/nova,alaski/nova,sridevikoushik31/nova,isyippee/nova,angdraug/nova,gooddata/openstack-nova,apporc/nova,Stavitsky/nova,Yusuke1987/openstack_template,cloudbau/nova,yrobla/nova,raildo/nova,iuliat/nova,qwefi/nova,mandeepdhami/nova,dstroppa/openstack-smartos-nova-grizzly,akash1808/nova_test_latest,adelina-t/nova,rrader/nova-docker-plugin,CEG-FYP-OpenStack/scheduler,vmturbo/nova,rahulunair/nova,rahulunair/nova,cloudbase/nova,blueboxgroup/nova,mikalstill/nova,akash1808/nova,dims/nova,jianghuaw/nova,petrutlucian94/nova_dev,petrutlucian94/nova,BeyondTheClouds/nova,dims/nova,rajalokan/nova,imsplitbit/nova,orbitfp7/nova,luogangyi/bcec-nova,JianyuWang/nova,barnsnake351/nova,mikalstill/nova,redhat-openstack/nova,sridevikoushik31/nova,zzicewind/nova,leilihh/nova,ewindisch/nova,double12gzh/nova,TieWei/nova,Juniper/nova,TwinkleChawla/nova,zaina/nova,raildo/nova,watonyweng/nova,Metaswitch/calico-nova,dawnpower/nova,cernops/nova,DirectXMan12/nova-hacking,yosshy/nova,felixma/nova,sebrandon1/nova,hanlind/nova,badock/nova,plumgrid/plumgrid-nova,cyx1231st/nova,bigswitch/nova,CiscoSystems/nova,TwinkleChawla/nova,tealover/nova,gspilio/nova,gooddata/openstack-nova,gspilio/nova,citrix-openstack-build/nova,ruslanloman/nova,fnordahl/nova,Yuriy-Leonov/nova,MountainWei/nova,vladikr/nova_drafts,ted-gould/nova,zhimin711/nova,JioCloud/nova_test_latest,vmturbo/nova,akash1808/nova,shail2810/nova,OpenAcademy-OpenStack/nova-scheduler,angdraug/nova,edulramirez/nova,tudorvio/nova,thomasem/nova,shootstar/novatest,mgagne/nova,CloudServer/nova,silenceli/nova,tealover/nova,jeffrey4l/nova,zhimin711/nova,fajoy/nova,shahar-stratoscale/nova,eonpatapon/nova,j-carpentier/nova,yrobla/nova,j-carpentier/nova,Yuriy-Leonov/nova,tianweizhang/nova,cloudbase/nova-virtualbox,shail2810/nova,Juniper/nova,JianyuWang/nova,bigswitch/nova,petrutlucian94/nova,zzicewind/nova,edulramirez/nova,openstack/nova,vmturbo/nova,tangfeixiong/nova,LoHChina/nova,hanlind/nova,Triv90/Nova,scripnichenko/nova,belmiromoreira/nova,virtualopensystems/nova,eharney/nova,belmiromoreira/nova,rickerc/nova_audit,spring-week-topos/nova-week,eayunstack/nova,noironetworks/nova,bclau/nova,projectcalico/calico-nova,kimjaejoong/nova,leilihh/nova,klmitch/nova,tangfeixiong/nova,mmnelemane/nova,ntt-sic/nova,CiscoSystems/nova,alvarolopez/nova,NeCTAR-RC/nova,Stavitsky/nova,JioCloud/nova,affo/nova,phenoxim/nova,sridevikoushik31/nova,hanlind/nova,dstroppa/openstack-smartos-nova-grizzly,devendermishrajio/nova,redhat-openstack/nova,sridevikoushik31/openstack,varunarya10/nova_test_latest,sebrandon1/nova,adelina-t/nova,SUSE-Cloud/nova,cyx1231st/nova,yatinkumbhare/openstack-nova,saleemjaveds/https-github.com-openstack-nova,takeshineshiro/nova,LoHChina/nova,devendermishrajio/nova,mahak/nova,tanglei528/nova,rickerc/nova_audit,MountainWei/nova,devoid/nova,JioCloud/nova_test_latest,shahar-stratoscale/nova,Yusuke1987/openstack_template,sridevikoushik31/nova,BeyondTheClouds/nova,devendermishrajio/nova_test_latest,tudorvio/nova,viggates/nova,mmnelemane/nova,Francis-Liu/animated-broccoli,yrobla/nova,plumgrid/plumgrid-nova,mahak/nova,felixma/nova,rajalokan/nova,klmitch/nova,mandeepdhami/nova,alvarolopez/nova,akash1808/nova_test_latest,vladikr/nova_drafts,cernops/nova,maelnor/nova,CloudServer/nova,Tehsmash/nova,mikalstill/nova,thomasem/nova,noironetworks/nova,iuliat/nova,eonpatapon/nova,nikesh-mahalka/nova,maheshp/novatest,alexandrucoman/vbox-nova-driver,projectcalico/calico-nova,CCI-MOC/nova,double12gzh/nova,ted-gould/nova,ruslanloman/nova,Metaswitch/calico-nova,Triv90/Nova,berrange/nova,mgagne/nova