connectivty log: log duplex state

Add detected changes of full/half duplex to connectivity.log

Bug-Url: https://bugzilla.redhat.com/1111234
Change-Id: I29745f7e6400cff9f0450273047480221e4e363e
Signed-off-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/30225
Reviewed-by: Francesco Romani <fromani@redhat.com>
Reviewed-by: Antoni Segura Puimedon <asegurap@redhat.com>