XATerminatorService needs jta/jts differentiation

The XATerminatorService hardcodes instantiation of a com.arjuna.ats.internal.jbossatx.jta.jca.XATerminator instance, which is correct for JTA mode operation but invalid for JTS (jtax) mode usage. For the latter, a com.arjuna.ats.internal.jbossatx.jts.jca.XATerminator instance in required instead. The service must take account of the mode the transaction system is running in and correctly select which class to instantiate.