[BROOKLYN-92] Configure brokerName for ActiveMQ

Issue raised in jira: https://issues.apache.org/jira/browse/BROOKLYN-92
I am torn on this one. I understand your point, yet I've been bit many times by such long timeout. If something goes wrong it wastes a lot of your time. However this is unrelated to the enhancement this patch proposes. If we ever wanted to talk about the merits of timeouts it can be done at a later time. Change reverted per your suggestion.