Quagga: Fix MPLS LSP scheduling to follow nexthop route update

Quagga: Fix MPLS LSP scheduling to follow nexthop route update

Fix LSP scheduling to occur only after routes are processed because
the LSP resolution depends on the nexthop route being selected. This
is similar to how NHT processing is scheduled.

Signed-off-by: Vivek Venkatraman <vivek@cumulusnetworks.com>
Reviewed-by:   Donald Sharp <sharpd@cumulusnetworks.com>
Reviewed-by: Daniel Walton <dwalton@cumulusnetworks.com>
Ticket: CM-6743
Reviewed By: CCR-3233
Testing Done: Verified the failed test multiple times.