ZOOKEEPER-1894. ObserverTest.testObserver fails consistently. (michim via camille)

git-svn-id: https://svn.apache.org/repos/asf/zookeeper/trunk@1582572 13f79535-47bb-0310-9956-ffa450edef68
Apply ZOOKEEPER-1891.

https://issues.apache.org/jira/secure/attachment/12634073/ZOOKEEPER-1891.patch
Apply ZOOKEEPER-1892.patch.

https://issues.apache.org/jira/secure/attachment/12634331/ZOOKEEPER-1892.patch
Apply ZOOKEEPER-1870.patch.

https://issues.apache.org/jira/secure/attachment/12635000/ZOOKEEPER-1870.patch