protocols/ovsdb: Handle disconnects gracefully

If the client closes the connection during setup, the socket's FD is
closed out automatically, ignore the errors while forcably shuting down
the socket.

Signed-off-by: Jason Kölker <jason@koelker.net>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

ryu/services/protocols/ovsdb/manager.py

@@ -92,7 +92,11 @@ class OVSDB(app_manager.RyuApp):
             self.send_event_to_observers(ev)
 
         else:
-            sock.shutdown(socket.SHUT_RDWR)
+            try:
+                sock.shutdown(socket.SHUT_RDWR)
+            except:
+                pass
+
             sock.close()
 
     def start(self):