Remove prov_vlan_id from baremetal

In nova, this parameter is not used
(and will be unacceptable soon)

Change-Id: I072a204bef49940fb2ddc8dc44480b570bc3212c
Additional "Unify Manager._update behaviour" cleanup

Make _update always return an instance of self.resource_class.

This is in preparation for fixing bug 1145768 by reverting the API
changes made in the original "Unify Manager._update behaviour" change.

This is to avoid needing to revert some of the cleanup that was made
in that change.

Change-Id: I842bda40a0dc168689a7dd8b88433c3cebef5839
Merge "Remove prov_vlan_id from baremetal"
Merge "Additional "Unify Manager._update behaviour" cleanup"