core: fix cpu profile validation on import VM

The cluster setting was missing on the VM object, thus we'll use the
destination cluster.

Change-Id: If228a9d2acd2db1a63bd9d12e798128dce6a3ee7
Bug-Url: https://bugzilla.redhat.com/1084930
Signed-off-by: Arik Hadas <ahadas@redhat.com>