Reuse a server instance in test_disk_config
Reuse a server instance in test_disk_config

In test_disk_config.py, each test creates a server instance everytime.
By applying this patch, a server instance is reused without a new server
creation if the existing server has necessary status.

Change-Id: I1e1f03df3b0d7840b6af666dbb412a7fea2ccbba

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