[#1011346] BUGFIX: Thread synchronization inside GetPooledConnector

Reworked UngetConnector to remove the connector from the Busy queue and add to the Available queue under the same lock.

Thanks Ilya G for the heads up.
Merge pull request #33 from franciscojunior/bug-1011346-thread-synchronization

[#1011346] BUGFIX: Thread synchronization inside GetPooledConnector

Bug report link: http://pgfoundry.org/tracker/?func=detail&atid=590&aid=1011346&group_id=1000140