qa: fix ConnectionFilter bug causing packets to be stuck after __exit__/remove

neo/tests/threaded/__init__.py

@@ -531,7 +531,8 @@ class ConnectionFilter(object):
                         break
                 else:
                     if conn.isClosed():
-                        return
+                        queue.clear()
+                    else:
                         # Use the thread that created the packet to reinject it,
                         # to avoid a race condition on Connector.queued.
                         conn.em.wakeup(lambda conn=conn, packet=packet: