Fix devstack engine test coverage
Fix devstack engine test coverage

One test per method with proper mocking. Add tests localrc generation

Change-Id: Id48e00f03909594b07c9763aa1aa01769bb0366d

varunarya10/rally,afaheem88/rally,gluke77/rally,openstack/rally,openstack/rally,cernops/rally,eayunstack/rally,gluke77/rally,vganapath/rally,eayunstack/rally,group-policy/rally,shdowofdeath/rally,eonpatapon/rally,redhat-openstack/rally,paboldin/rally,go-bears/rally,vponomaryov/rally,pyKun/rally,group-policy/rally,aforalee/RRally,pandeyop/rally,vponomaryov/rally,aplanas/rally,cernops/rally,pandeyop/rally,group-policy/rally,eonpatapon/rally,shdowofdeath/rally,yeming233/rally,paboldin/rally,vganapath/rally,vganapath/rally,aforalee/RRally,openstack/rally,afaheem88/rally,vganapath/rally,gluke77/rally,aplanas/rally,amit0701/rally,paboldin/rally,vefimova/rally,go-bears/rally,amit0701/rally,gluke77/rally,pyKun/rally,eayunstack/rally,ytsarev/rally,varunarya10/rally,vefimova/rally,ytsarev/rally,redhat-openstack/rally,openstack/rally,amit0701/rally,yeming233/rally