Default connector is hardcoded in JMS connection factory definition

When JMS connection factory definitions are used to setup connection factory, the messaging subsystem adds the "netty" connector if no connectors are specified in the definition.

This introduces a problem if users do not define a connector named "netty" in their configuration (as it will be the case when we switch to using the http-connector instead of the remote-connector by default).

Workaround this is to ask HornetQ for the connectors that can be used and pick one (and logs a warning message telling the user that it should not depend on that behaviour and explicitly specify which connector to use).