AMQP-281 Shut Down Timer in AMQP Appender

When using the AMQP log4j appender, it
can cause orphaned daemon threads when undeploying WARs.

Also, when exiting main() methods, apps should call
Log4jConfigurer.shutdownLogging(); in a finally block
to destroy() the connetion factory (releasing threads
used by the rabbit client).

__cherry-pick to 1.1.x__