[chiptest] Network-independent RPC server shutdown (#15954)

Terminating app-register RPC server with the usage RPC call itself
might cause troubles in case when the network connection is not
reliable (e.g. no route to the server). This commit simplifies the
shutdown process by using dedicated shutdown method.

scripts/tests/chiptest/accessories.py

@@ -15,7 +15,6 @@
 
 import sys
 import threading
-from xmlrpc.client import ServerProxy
 from xmlrpc.server import SimpleXMLRPCServer
 
 IP = '127.0.0.1'
@@ -98,9 +97,6 @@ def waitForOperationalAdvertisement(self, name):
             return accessory.waitForOperationalAdvertisement()
         return False
 
-    def ping(self):
-        return True
-
     def __startXMLRPCServer(self):
         self.server = SimpleXMLRPCServer((IP, PORT))
 
@@ -114,20 +110,9 @@ def __startXMLRPCServer(self):
         self.server.register_function(
             self.waitForOperationalAdvertisement,
             'waitForOperationalAdvertisement')
-        self.server.register_function(self.ping, 'ping')
 
-        self.server_thread = threading.Thread(target=self.__handle_request)
+        self.server_thread = threading.Thread(target=self.server.serve_forever)
         self.server_thread.start()
 
-    def __handle_request(self):
-        self.__should_handle_requests = True
-        while self.__should_handle_requests:
-            self.server.handle_request()
-
     def __stopXMLRPCServer(self):
-        self.__should_handle_requests = False
-        # handle_request will wait until it receives a message,
-        # so let's send a ping to the server
-        client = ServerProxy('http://' + IP + ':' +
-                             str(PORT) + '/', allow_none=True)
-        client.ping()
+        self.server.shutdown()