Don't pass disk config as None. Fix for bug 980119
Don't pass disk config as None. Fix for bug 980119

Change-Id: Iebf920114454eaae9d250df51e4a4c219786fcda

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