ZOOKEEPER-1660 Documentation for Dynamic Reconfiguration (Reed Wanderman-Milne via shralex)

git-svn-id: https://svn.apache.org/repos/asf/zookeeper/trunk@1621313 13f79535-47bb-0310-9956-ffa450edef68
ZOOKEEPER-1936 Server exits when unable to create data directory due to race