Porting existing VPLS LDP MAC flush in PBB VPLS

Both the I-VPLS and B-VPLS components inherit the LDP MAC flush capabilities of a regular VPLS to fast age the related FDB entries for each domain: C-MACs for I-VPLS and B-MACs for B-VPLS. Both types of LDP MAC flush are supported for I-VPLS and B-VPLS domains:

In addition, only for the B-VPLS domain, changing the backbone source MAC of a B-VPLS triggers an LDP MAC flush-all-from-me to be sent in the related active topology. At the receiving PBB PE, a B-MAC flush automatically triggers a flushing of the C-MACs associated with the old source B-MAC of the B-VPLS.