network manager returns empty list, not raise an exception
network manager returns empty list, not raise an exception

Fix bug #1023805

Change-Id: I9ddb10db127375ad37a7760b53e44782b392c2e3

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