engine: Don't log unsynchronized unmanaged networks

If the network is not synchronized, it should be logged only if it's
managed. Otherwise, it's of no interest to us.

Change-Id: I7b8a582134f5c9d37d64bcd5970f2f3bfb24ab20
Bug-Url: https://bugzilla.redhat.com/906393
Signed-off-by: Mike Kolesnik <mkolesni@redhat.com>