Warn about using embedded JMS broker during pre-launch config

The messaging.sh used by EAP CD and EAP on OS 7.2 adds the embedded artemis broker by default, only omitting it if the env vars that turn on remote AMQ integration are set.

But use of the embedded broker is noted as being unsupported in the CD docs[1] and is something we intend to drop in future releases, i.e. in CD 15 or 16 and EAP on OS 7.3.

But we can be a bit more vocal about this now, i.e. by a log_warn from messaging.sh if it adds the embedded broker config.

Perhaps we can also let users disable adding the embedded broker via an env var, which gives them a way to turn off the warn and also lets them remove an expense resource from their server.

In EAP on OS 7.3 we may need an opposite env var to turn on adding the embedded broker, as a compatibility aid so users who insist on having it don't need to bring their own standalone.xml. That's not part of this though.

[1] https://access.redhat.com/documentation/en-us/jboss_enterprise_application_platform_continuous_delivery/13/html/getting_started_with_jboss_eap_for_openshift_online/introduction#comparison_eap_and_xpaas_eap_image