Testing multiple priority donation.
If the statements printed below are all true, you pass.
 1. Main thread should have priority 30.  Actual priority: 30.
 2. Main thread should have priority 31.  Actual priority: 31.
 3. Thread b acquired lock b.
 4. Thread b finished.
 5. Thread b should have just finished.
 6. Main thread should have priority 30.  Actual priority: 30.
 7. Thread a acquired lock a.
 8. Thread a finished.
 9. Thread a should have just finished.
10. Main thread should have priority 29.  Actual priority: 29.
Multiple priority priority donation test finished.