Files that control ownership have special ownership rules, to disallow
someone from self-approving a CL that adds themselves to a file that
controls ownership. owners.py now requires that they be named OWNERS or
end with a suffix of _OWNERS to ensure the special ownership rules are
correctly applied.

Bug: 801315
Change-Id: I083a2d15bdc9c749e3838fb1c983286d5a7c4af9
Reviewed-on: https://chromium-review.googlesource.com/1204917Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>