Race condition in InboundJmsResourcePool.java causes inbound message processing to halt

A race condition in com.sun.genericra.inbound.async.InboundJmsResourcePool.java can cause all inbound message processing on the queue associated with a particular pool instance to halt; processing on this queue will not resume until the affected application server is restarted.

MDBs configured with a MaxPoolSize of 1 are particularly vulnerable, as are queues receiving bursty traffic where messages sometimes arrive in considerable numbers faster than the MDB can process them. The onMessage() execution time also plays a role. The bug can manifest itself randomly within minutes, hours, or many days after startup. In clustered configurations, each server is separately and independently vulnerable to the race.

The race condition is triggered when the MQS driver, seeing a new message in the inbound queue, calls getServerSession() in one thread at the same time when a worker thread tries to release a ServerSession instance (= InboundJmsResource instance) back to the pool. In the problematic scenario, the resource is successfully marked as free, and connectionsInUse decremented, by the second thread; but the first thread, having found the pool exhausted a moment earlier, creates a PauseObject and puts itself on the pool's waitQ after the second thread has found the waitQ empty, and thus the first thread is never notified of the freed resource. This outcome can be verified in a heap dump; the only indication in the server log is that a "Notifying the thread" at level FINE is _not_ logged.

I am going to attach a proposed fix. This also subsumes a fix for #56 (which had arisen at an earlier point of the same incident investigation).
#### Environment
Seen both with GlassFish 2.1.1-p17 through -p21, GenericJMSRA as bundled with this (= 2.0.1 from mid 2009), and with GlassFish 3.1.2.6, GenericJMSRA 2.1b, on Linux (SLES10SP2 and SLES11SP1) x86_64, and using the IBM MQS driver 7.0.1.6\. By inspection, the bug has existed since inception of the code.
#### Affected Versions
[0.9, 1.0a, 1.0, v1.5, 1.5, v1.6, 1.6, 2.1a, 2.1b, current, 2.2a]