Revert "Remove MGS policy overrides when they have cloud values"

This reverts commit 6a139b5b.

Reason for revert: Looks like this broke the buildbot: https://ci.chromium.org/p/chromium/builders/ci/Linux%20ChromiumOS%20MSan%20Tests/24164
https://ci.chromium.org/p/chromium/builders/ci/Linux%20ChromiumOS%20MSan%20Tests/24165
https://ci.chromium.org/p/chromium/builders/ci/Linux%20ChromiumOS%20MSan%20Tests/24166
https://ci.chromium.org/p/chromium/builders/ci/Linux%20ChromiumOS%20MSan%20Tests/24167

Original change's description:
> Remove MGS policy overrides when they have cloud values
>
> Bug: b:186736957
> Change-Id: I9f0cbfdbcfa4d7713d55446f17058a35f9ad94c2
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2983202


> Commit-Queue: Maria Petrisor <mpetrisor@chromium.org>
> Reviewed-by: Dominique Fauteux-Chapleau <domfc@chromium.org>
> Reviewed-by: Alexander Hendrich <hendrich@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#899021}

Bug: b:186736957
Change-Id: I1bb56eafdfb680c3eb5158017d648a93674ada80
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3011483


Auto-Submit: Scott Little <sclittle@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Scott Little <sclittle@chromium.org>
Reviewed-by: Dominique Fauteux-Chapleau <domfc@chromium.org>
Owners-Override: Scott Little <sclittle@chromium.org>
Cr-Commit-Position: refs/heads/master@{#899186}