mrpd enhancements

Small enhancements

Client notification when declaration is emitted on the wire

If a VLAN needs to be declared and "on the wire" before a TA that uses that VLAN can be declared, there should be a mechanism for notifying the client when the attrib is emitted out the network port. Currently the time to emit a VLAN declaration is subject to the join timer running, so an mrpd client has no knowledge of when an attribute is actually emitted.

One suggested fix is to have mrpd NEVER emit a TA before a VLAN is declared. Would need some sort of timeout on this though because the client needs to know if a TA never appears on the wire.

Large enhacements