Prevent re-entrant walks on an adjacency.
The re-entrant walks were caused when the walk from an IP adj updated a fib_netry with an MPLS adj which in turn triggers a walk of the IP adj. Re-entrant walks do unnecessary work.
also fixed a walk merge issue where the encountered walk should only be checked for equivalence woth the most recent alk, not any in the list. Otherwise an UO,DOWN,UP beceoms (2*)UP,DOWN
Change-Id: Ib8b27f055dc6c1366d33740276d1c26cd314220a
Signed-off-by: Neale Ranns <[email protected]>