Simplify parse_image_id.
Simplify parse_image_id.

Change-Id: I7915e7a9f252da84fa76cec282c546444afa7c59

vedujoshi/os_tempest,NexusIS/tempest,izadorozhna/tempest,xbezdick/tempest,afaheem88/tempest,itskewpie/tempest,manasi24/jiocloud-tempest-qatempest,redhat-cip/tempest,LIS/lis-tempest,cisco-openstack/tempest,CiscoSystems/tempest,izadorozhna/tempest,pandeyop/tempest,zsoltdudas/lis-tempest,dkalashnik/tempest,jamielennox/tempest,Tesora/tesora-tempest,vmahuli/tempest,neerja28/Tempest,cloudbase/lis-tempest,queria/my-tempest,eggmaster/tempest,alinbalutoiu/tempest,Tesora/tesora-tempest,cloudbase/lis-tempest,citrix-openstack-build/tempest,hayderimran7/tempest,varunarya10/tempest,vmahuli/tempest,roopali8/tempest,rakeshmi/tempest,ntymtsiv/tempest,tonyli71/tempest,FujitsuEnablingSoftwareTechnologyGmbH/tempest,Juniper/tempest,masayukig/tempest,citrix-openstack/build-tempest,pczerkas/tempest,yamt/tempest,bigswitch/tempest,pandeyop/tempest,jaspreetw/tempest,afaheem88/tempest,Juraci/tempest,itskewpie/tempest,NexusIS/tempest,danielmellado/tempest,Vaidyanath/tempest,openstack/tempest,Mirantis/tempest,manasi24/jiocloud-tempest-qatempest,neerja28/Tempest,eggmaster/tempest,hpcloud-mon/tempest,Lilywei123/tempest,Mirantis/tempest,ebagdasa/tempest,FujitsuEnablingSoftwareTechnologyGmbH/tempest,nunogt/tempest,rzarzynski/tempest,afaheem88/tempest_neutron,xbezdick/tempest,rakeshmi/tempest,vedujoshi/tempest,LIS/lis-tempest,cisco-openstack/tempest,Vaidyanath/tempest,BeenzSyed/tempest,flyingfish007/tempest,vedujoshi/tempest,armando-migliaccio/tempest,hpcloud-mon/tempest,manasi24/tempest,manasi24/tempest,nunogt/tempest,jaspreetw/tempest,yamt/tempest,pczerkas/tempest,Juraci/tempest,danielmellado/tempest,redhat-cip/tempest,CiscoSystems/tempest,ntymtsiv/tempest,sebrandon1/tempest,tudorvio/tempest,akash1808/tempest,adkerr/tempest,armando-migliaccio/tempest,bigswitch/tempest,flyingfish007/tempest,ebagdasa/tempest,hayderimran7/tempest,JioCloud/tempest,openstack/tempest,masayukig/tempest,adkerr/tempest,afaheem88/tempest_neutron,alinbalutoiu/tempest,zsoltdudas/lis-tempest,akash1808/tempest,vedujoshi/os_tempest,tonyli71/tempest,varunarya10/tempest,rzarzynski/tempest,tudorvio/tempest,citrix-openstack-build/tempest,queria/my-tempest,Lilywei123/tempest,jamielennox/tempest,BeenzSyed/tempest,roopali8/tempest,JioCloud/tempest,Juniper/tempest,citrix-openstack/build-tempest,sebrandon1/tempest,dkalashnik/tempest