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This CL rolls back the unified consent preferences when
the installation is excluded from the experiment. This is
needed in case the unified consent feature has to be disabled
due to some reason and rolled out again later.

During rollback, the following is done:
 - All unified consent prefs are cleared.
 - Sync-everything is turned back on if all datatypes are
 turned on and if the consent bump was supposed to be presented.

Bug: 863937
Change-Id: Icb58fad008069c0b38a1ef952ed19e48f8cd3fe6
Reviewed-on: https://chromium-review.googlesource.com/1165226
Commit-Queue: Thomas Tangl <tangltom@chromium.org>
Reviewed-by: Mihai Sardarescu <msarda@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582263}