MINOR: connection: also stop receiving after a SOCKS4 response

Just as is done in previous patch for all handshake handlers,
also stop receiving after a SOCKS4 response was received. This
one escaped the previous cleanup but must be done to keep the
code safe.
diff --git a/src/connection.c b/src/connection.c
index 8b0851f..361f2ee 100644
--- a/src/connection.c
+++ b/src/connection.c
@@ -1166,6 +1166,7 @@
 	} while (0);
 
 	conn->flags &= ~CO_FL_SOCKS4_RECV;
+	__conn_sock_stop_recv(conn);
 	return 1;
 
  not_ready: