JMS: Change in behavior of the default user identifier value

Change caused when using CLIENT transport for a channel that does not have a security exit defined.

From IBM® WebSphere® MQ 7.1, if an IBM WebSphere MQ classes for JMS application is connecting to a queue manager, using the CLIENT transport through a channel that does not have a security exit defined, and no user identifier is specified, by calling ConnectionFactory.createConnection(), the IBM WebSphere MQ classes for JMS application queries the value of the Java System Property user.name and passes this to the queue manager for authorization as part of the call to create a connection from a connection factory object. This behavior also occurs when calling ConnectionFactory.createConnection(String, String) and passing a blank or null value for the first parameter userID.

If the user specified by the Java System Property user.name is not authorized to access the queue manager, a JMSException containing Reason Code MQRC_NOT_AUTHORIZED is thrown.