Fix physical_resource_name for Nova server

This patch fixes the problem caused by the overridden
physical_resource_name() in OS::Nova::Server resource.  If the name
assigned to the Server resource is used for Keystone user creation,
there is a higher possibility of name conflicts.

Change-Id: I5eff496aef8949db9c1f9865e8de33d2b58c7a7f
Closes-Bug: #1324499
Merge "Fix physical_resource_name for Nova server"