[WFLY-3883] use a LIST for the JMS connection-factory's connector attribute

and for the pooled-connection-factory too.

* for legacy versions, the LIST of STRING is converted to a MAP by the
  messaging transformers
* the attribute defines a value converter to ensure than legacy
  operations (that uses a MAP) can still be executed on the latest
  version.

JIRA: https://issues.jboss.org/browse/WFLY-3883
This is the problem. In your comment you noted, "The current code already works as you suggest: the attribute is a map but we also accept a LIST and convert it to the bogus map."  But this is a LIST. 

I think you could meet your objective of easing CLI us eeasily enough by going back to SimpleMapAttributeDefinition and then reworking the ParameterCorrector a bit.  

I don't think MapAttributeDefinition.LIST_TO_MAP_CORRECTOR will work for this, as it will  convert ["in-vm","other"] to { "in-vm" => "other"}.