engine: Vnic live update should be blocked if pm enabled

Any vnic live update action should be blocked either if
the new profile is marked for port mirroring or if the
existing profile is configured with port mirroring.
Such change requires unplugging and plugging the vnic.

Change-Id: I5101e769d33db8b1fa2cfcd0ab0bd766fd9ac13f
Bug-Url: https://bugzilla.redhat.com/1045079
Signed-off-by: Moti Asayag <masayag@redhat.com>