packaging: setup: cluster comp. level as max common between vdsm and engine

During alpha release the VDSM maximum supported cluster level
will not necessarily matches the engine one.
Choosing the max common between them.

Change-Id: Iaf1b04e7c087ef70ccceb83fdbff8caf7e2942e2
Bug-Url: https://bugzilla.redhat.com/1100236
Signed-off-by: Simone Tiraboschi <stirabos@redhat.com>