ldpd: fix sporadic failures in the ldp-topo1 topotest

ldpd: fix sporadic failures in the ldp-topo1 topotest

Commit 220e848cc5 introduced an optimization that would prevent ldpd
from sending redundant label mappings when it receives notifications
from zebra about routes that didn't effectively change (such
notifications can happen under certain circumstances).

The problem is that that commit didn't take into account the metric
of the received routes, so it would dismiss a notification of a
route with a better metric taking the place of another route in the
RIB, preventing the newly selected route from receiving the label
mappings it needs.

Revert 220e848cc5 temporarily to fix sporadic failures in the CI
system until we have a better solution.

Debugged-by: Lynne Morrison lynne@voltanet.io
Signed-off-by: Renato Westphal <renato@opensourcerouting.org>