PW control channel status request mechanism

The system implements an optional PW control channel status request mechanism. This enhances the existing control channel status mechanism so that a peer that has a "stale" PW status for the far-end of a PW can request that the peer PE send a static PW status update. Accurate and current information about the far end status of a PW is important for correct operation of PW redundancy. This mechanism ensures a consistent view of the control plane is maintained, as far as possible, between peer nodes. It is not intended to act as a continuity check between peer nodes.