MULE-7731 JMS transport should reuse javax.jms.Session, javax.jms.Messag...

...eProducer instances by default
We own JmsSupport, so we can add a new method to know whether or not we can cache their connections. My concern on this code is that if we add another JmsSupport implementation we would have to remember to come here and review this line. But, if the JmsSupport has a supportsCaching, then it will be pretty straightforward to do the right thing there.