rename _libvirtNets2vdsm as it is used publicly

Change-Id: I7c821887a6e72119077bcd3d57a395306ab33a9a
Signed-off-by: ibarkan <ibarkan@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/35925
Reviewed-by: Ondřej Svoboda <osvoboda@redhat.com>
Tested-by: Ondřej Svoboda <osvoboda@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>