The value of svcTlsPropagateMacFlush specifies whether
'MAC flush' messages received from the given LDP are
propagated to all spoke-SDPs and mesh-SDPs within the
context of this VPLS service. The propagation will follow
the 'split-horizon' principle and any data-path blocking in
order to avoid the looping of these messages.
The value of 'true' enables the propagation.