Set daemon = True on the thread in the SMTP test server running while

running tests. This fixes the annoying problem of the python process
staying alive after certain bugs in the test invocation or after a
plain Ctrl + c.
 - Legacy-Id: 10718

ietf/utils/test_smtpserver.py

@@ -14,7 +14,8 @@ def start(self):
         """Start the listening service"""
         self.exit_condition = []
         kwargs={'exit_condition':self.exit_condition,'timeout':1.0} 
-        self.thread = threading.Thread(target=self.wrap_loop,kwargs=kwargs )
+        self.thread = threading.Thread(target=self.wrap_loop, kwargs=kwargs)
+        self.thread.daemon = True
         self.thread.start()     
 
     def stop(self):