Fix XML response for return_reservation_id.
Fix XML response for return_reservation_id.

The XML serializer for create uses the server template for it's response.
However, when return_reservation_id is set, only a reservation_id is
going to be returned.

To enable the XML response to be serialized the reservation id is now
returned in a server tag/object.

This commit fixes bug 1061124

Change-Id: Ic74071b1d527c3f3752e296d3fd46a28a99beb76
Signed-off-by: Matthew Treinish <17bfc8751a60276d19cd7f0cbe3763e22d3e07a0@linux.vnet.ibm.com>
(cherry picked from commit 903b51e148c2f9e858b5ea0ca5b230ac308d76c5)

paulmathews/nova,paulmathews/nova,paulmathews/nova