Fix link Monitor unpack error and device retrieval

Change-Id: I57f28ae08d338f73aa6a64a995ecb954a95ac048
Signed-off-by: Antoni S. Puimedon <asegurap@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/20463
Reviewed-by: Dan Kenigsberg <danken@redhat.com>