Replaced Statement with PreparedStatement.
Nearly all X.close() are now in DBConnectionManager.
Also improved if{..}else{..} logic (human/compiler hint, usually if{..} should/will be executed).

git-svn-id: http://svn.igniterealtime.org/svn/repos/openfire/trunk@11691 b35dd754-fafc-0310-a699-88a17e54d16e