NSR for Egress P2MP LSP

This feature extends the nonstop active routing (NSR) support to RSVP point-to-multipoint (P2MP) egress LSPs. During the switchover, the LSP comes up on the backup Routing Engine that shares and synchronizes the state information with the primary Routing Engine before and after the switchover. The NSR support for P2MP egress LSPs ensures that the switchover remains transparent to the network neighbors and preserves the LSP information across the switchover.