netinfo: Return Mac of bond slaves in lower case

getVdsCaps returns MAC of all interfaces in lower case and for bond slaves
it returned it in upper cases - fixing inconsistency

Change-Id: Ibbd431b73fa1f381a897b6550e2b398009c0a7b9
Bug-Url: https://bugzilla.redhat.com/1116810
Signed-off-by: Genadi Chereshnya <gcheresh@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/31888
Reviewed-by: Dan Kenigsberg <danken@redhat.com>