cros: Remove extraneous ash:: from ash/login.

Also remove a LOG(ERROR) that was accidentally committed.

Bug: 719015
Change-Id: Ib4564903b358cdba5c1189a5b9fac484e7c8ad16
Reviewed-on: https://chromium-review.googlesource.com/663667


Commit-Queue: Jacob Dufault <jdufault@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501355}