[CrOS MultiDevice] Fix an error in FakeCryptAuthEnrollmentManager.

Once enrollment has completed successfully, enrollment should be
considered valid.

Bug: 824568, 752273
Change-Id: I5c7e209df750af48b2d4002a6fc308bbbeb0e1c0
Reviewed-on: https://chromium-review.googlesource.com/1006216
Commit-Queue: Kyle Horimoto <khorimoto@chromium.org>
Commit-Queue: Ryan Hansberry <hansberry@chromium.org>
Reviewed-by: Ryan Hansberry <hansberry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#549729}

components/cryptauth/fake_cryptauth_enrollment_manager.cc

@@ -22,6 +22,7 @@ void FakeCryptAuthEnrollmentManager::FinishActiveEnrollment(
 
   if (success) {
     last_enrollment_time_ = enrollment_finish_time;
+    is_enrollment_valid_ = true;
     is_recovering_from_failure_ = false;
   } else {
     is_recovering_from_failure_ = true;