Added a shutdown_client method on SimpleRpcServer manager to disconnect a...

Added a shutdown_client method on SimpleRpcServer manager to disconnect a client before to calling the disconnection callback.

sjrpc/server/simple.py

@@ -41,6 +41,9 @@ class SimpleRpcServer(ConnectionManager):
             connection.shutdown(self._on_disconnect)
         self._listening_sock.close()
 
+    def shutdown_client(self, connection):
+        connection.shutdown(callback=self._on_disconnect)
+
     def all_connections(self):
         return set(self._clients.values())