engine : Changing cluster during oVirtNode approve throws unsupported CPU exception

Changing oVirt node cluster during approve host
causes failure with error "Host CPU type is not
supported in this cluster compatibility version
or is not supported at all"

Change-Id: I6f485ce0512ae9c35be5b3f803b7ca1c35dea4f9
Bug-Url: https://bugzilla.redhat.com/1079834
Signed-off-by: Ravi Nori <rnori@redhat.com>