Depending on visitation order the LoadElimination might be find memoized
nodes in its state tables that were killed by other reducers in the mean
time. The LoadElimination must just ignore those stale entries.

Bug: chromium:820820
Change-Id: Ia62e401ff77da547ed215a14074e70aeb5c3a766
Reviewed-on: https://chromium-review.googlesource.com/958843Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51892}