Keep adding owners in the order suggested by Gerrit until coverage is
achieved instead of finding a minimal set of owners, as that takes too
long

Bug: 1186420
Change-Id: Id2ab172db0b2e83ab950191958813163099181be
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2751343Reviewed-by: Josip Sokcevic <sokcevic@google.com>
Reviewed-by: Gavin Mak <gavinmak@google.com>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
Auto-Submit: Edward Lesmes <ehmaldonado@chromium.org>