engine: Block setup of mgmt net for older clusters

The old VDSMs don't work well when running setup networks right after
install (3.1) or they don't have setup networks verb (3.0) so added
FeatureSupported for this.

Old cluster versions will have hosts installed the old way (using the
ovirt-host-deploy method).

Change-Id: I690063e7d3ae72b4791894dabc59a7b3a6cd6a44
Bug-Url: https://bugzilla.redhat.com/985027
Signed-off-by: Mike Kolesnik <mkolesni@redhat.com>