Fix Bug 443142 - Deadlocked 'MQTT Rec': When 'MQTT Call:' Dies

The root cause is the CommsCallback.messageArrived, the while condition will never be false
when the messageQueue is full and not quiescing, even when the callback thread is trying to stop.
Fixed by checking the running flag in CommsCallback.messageArrived.

Bug: 443142
Signed-off-by: bzhangxmt <zhbinbj@cn.ibm.com>