Suppress test 1931 flakes caused by spurious wakeups

This is the same as the fix for test 1932 from commit
7aee63e49dc1421c7840de091bba04f5cf1a87e5 but for test 1931.

Spurious 'wait' wakeups can cause locks to appear contended when they
otherwise wouldn't be. This could make test 1931 somewhat flaky since
it could see contention in these cases. To prevent this flakiness this
suppresses output when these operations take place. This should not
affect the tests usefulness since those portions are mainly about
testing waiting behavior.

Test: ./test.py --host
Bug: 149308087
Change-Id: I8583b5f8a0665556d1562f62bd69728eccf9412b
1 file changed