ZOOKEEPER-2032. Cleaning up resources in ReconfigBackupTest (Hongchao Deng via shralex)

git-svn-id: https://svn.apache.org/repos/asf/zookeeper/trunk@1623916 13f79535-47bb-0310-9956-ffa450edef68
ZOOKEEPER-1936 Server exits when unable to create data directory due to race