naming enumeration not closed in some cases

Some times, ldap threads are not returning in the pool. They are attempting to read data from their sockets.
That problem is well described at http://blogs.warwick.ac.uk/kieranshaw/entry/ldap_connection_pooling/.
We need to enforce naming enumeration uses by adding a finally block for closing.

NamingEnumeration x = ...;
try {
 ...
} finally {
  x.close();
}

Here is the list of classes being impacted : LDAPSession,LDAPReference,LDAPTreeReference,LDAPFilterMatcher.