OK, tried the following so far:
1. cluster.url file listed in the config.properties file -- MQ reads this file on startup, but the java CLI options override the settings from this file, so setting the masterbroker there doesn't work.
2. Setting the "addtional properties" at the bottom of the "Configuration -> JMS" page in the admin console. Had to leave off the "-D", but it took the "imq.cluster.masterbroker" setting and then promptly ignored it.
3. Setting the "Start Arguments" as suggested. I was sure that this was going to work. I put "-Dimq.cluster.masterbroker=mq://app-a:37676/" there and it did add that option to the argument list, but it ended up having two masterbroker settings, and of course the one I put in was the first one and was then overridden by the second (incorrect) one.
I also noticed that every day that I go in and restart the A node to test these different settings, I get a different masterbroker, first D, then C, and today it is B. Very strange.
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