The finder.owners_queue contains a set of owners but they appear in an
arbitrary order on each invocation of the test. The current method of
assertEqual() with a list fails randomly because of the ordering being
different.

Example: https://ci.chromium.org/p/infra/builders/try/Depot%20Tools%20Presubmit%20(win)/b8897976148721436512

This changes comparisons of owners_queue to use an assertEqualSets()
which does a comparison that is order-independent.

Change-Id: Ia827795af283dadeb56f76ae0cf14fa4ad7e9eeb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1895699Reviewed-by: Aaron Gable <agable@chromium.org>
Reviewed-by: Garrett Beaty <gbeaty@chromium.org>
Commit-Queue: danakj <danakj@chromium.org>