Use primitive object while create nova client Server object

We need to use primitive object while create nova client Server object
instead of directly using nova.object.Instance object, because the
Server object construction will mess up the nova.object.Instance change
fields, that will result in the db updating operation will not update
the field like "updated_at".

Closes-Bug: #1365895
Change-Id: Ifc8e41c753b5fa2fa73d1eb1a4c02cdcec363460
Merge "Use primitive object while create nova client Server object"