Verify exact match for volume metadata update.
Verify exact match for volume metadata update.

Test_update_volume_metadata completely replaces a volume's existing
metadata with a new set, discarding any existing values.  Change the
assertion check to an exact match, not merely contains(), to ensure
that no stale metadata is present after update_all.

Change-Id: I1d363cfa65cb7c76fae9cfabaa499dcdf7c8b0ca
Closes-Bug: 1459351

varunarya10/tempest,rakeshmi/tempest,flyingfish007/tempest,pczerkas/tempest,Juraci/tempest,masayukig/tempest,cisco-openstack/tempest,tonyli71/tempest,JioCloud/tempest,pandeyop/tempest,tonyli71/tempest,nunogt/tempest,JioCloud/tempest,bigswitch/tempest,bigswitch/tempest,roopali8/tempest,rakeshmi/tempest,hayderimran7/tempest,afaheem88/tempest,sebrandon1/tempest,redhat-cip/tempest,alinbalutoiu/tempest,zsoltdudas/lis-tempest,dkalashnik/tempest,NexusIS/tempest,hayderimran7/tempest,cisco-openstack/tempest,Juniper/tempest,manasi24/jiocloud-tempest-qatempest,LIS/lis-tempest,zsoltdudas/lis-tempest,varunarya10/tempest,openstack/tempest,NexusIS/tempest,manasi24/tempest,vedujoshi/tempest,neerja28/Tempest,xbezdick/tempest,Tesora/tesora-tempest,flyingfish007/tempest,vedujoshi/tempest,LIS/lis-tempest,sebrandon1/tempest,tudorvio/tempest,openstack/tempest,izadorozhna/tempest,nunogt/tempest,jaspreetw/tempest,yamt/tempest,Tesora/tesora-tempest,masayukig/tempest,manasi24/tempest,manasi24/jiocloud-tempest-qatempest,xbezdick/tempest,tudorvio/tempest,yamt/tempest,akash1808/tempest,pandeyop/tempest,pczerkas/tempest,redhat-cip/tempest,alinbalutoiu/tempest,izadorozhna/tempest,Juraci/tempest,afaheem88/tempest,Juniper/tempest,neerja28/Tempest,roopali8/tempest,akash1808/tempest,dkalashnik/tempest,jaspreetw/tempest