Determine how to handle activemq-ra.rar in EAP 7.2 images

As part of the move to basing on AMQ 7 instead of 6 (CLOUD-2531), EAP CD removed the os-eap-activemq-rar module from the CD image.yaml, which means activemq-rar.rar no longer copied into standalone/deployments.

We need to decide how we want to handle this for EAP on OS 7.2, to which EAP on OS 7.1 users may want to migrate. Possibilities:

1) Always install the rar (just bring back the use of os-eap-activemq-rar module.)

2) Look at the messaging.sh script and perhaps if as part of its manipulation it sees the user is configuring remote connectivity to AMQ 6, add copying in the rar as well. (This might be appropriate for CD as well.)

3) Just don't include the rar and require users to bring it themselves. (This seems an unlikely option.)

4) Some better idea someone like jmesnil has.