Fix javadoc warnings.
Fixup findbugs warnings mostly by adding annotations saying 'working as expected'.
In RpcRetryingCallerWithReadReplicas made following change which findbugs spotted:
- if (completed == null) tasks.wait();
+ while (completed == null) tasks.wait();
In RecoverableZooKeeper, made all zk accesses synchronized -- we were doing it
half-ways previously.
In RatioBasedCompactionPolicy we were making an instance of Random on
each invocation of getNextMajorCompactionTime
43301167db