Update policy presubmit to prevent it from running twice

When //components/policy/resources and //chrome/test/data/policy or
//components/policy/tools both changed, only run the presubmit once

Bug: 1171839
Change-Id: I70be48e0892c1371612b84a81c908e7878c21d5a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2658512


Reviewed-by: Julian Pastarmov <pastarmovj@chromium.org>
Commit-Queue: Owen Min <zmin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#849133}