[Sahara] cleanup clusters correctly
[Sahara] cleanup clusters correctly

Cleaning up clusters w/o waiting until a cluster is completely removed
may cause different side-effects. For example floating ips may leave
allocated to a tenant which then is deleted by other clean ups. The ips
the cannot be removed. The same applies to security groups.

Change-Id: I8c82d2a6aad2398aa48f34285a6e0ab61c6bc1fe

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