Possible Memory leaks in PubSubPersistenceManager

http://www.igniterealtime.org/community/message/195174

There are two possible memory leaks in PubSubPersistenceManager.

1. In the function updateNode, the prepared statement needs to be closed pstmt.close(); on line 301.

2. In the function loadNodes, the prepared statement is not closed. on line 521 pstmt.close().