Stop using ProfileSyncService::RequestStop in tests

These were the last usages outside of SyncUserSettingsImpl and
ProfileSyncService itself.

Bug: 884159
Change-Id: I5a7a442f0c0fcea08f520601f8ead83f620ad4df
Reviewed-on: https://chromium-review.googlesource.com/c/1360635
Reviewed-by: Mohamed Amir Yosef <mamir@chromium.org>
Commit-Queue: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#613905}
10 files changed