netinfo: drop generally unused NetInfo.getNicBondings

getNicBondings was only used as a rather verbose convenience method
for getNicBonding. It is better to just have a simplified version
inside getNicBonding.

Change-Id: I8dc5c975dfab2917fe637012e31b3a83456f3c24
Signed-off-by: Antoni S. Puimedon <asegurap@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/29602
Reviewed-by: Dan Kenigsberg <danken@redhat.com>