unix-socket: fix memory leak on client disconnect

If a client loses the connection during a reload it initiated there is
a small memory leak.

Bug: #7891.
(cherry picked from commit f963c408bd)

src/unix-manager.c

@@ -519,7 +519,7 @@ static int UnixCommandExecute(UnixCommand * this, char *command, UnixClient *cli
     }
 
     if (UnixCommandSendJSONToClient(client, server_msg) != 0) {
-        goto error;
+        goto error_cmd;
     }
 
     json_decref(jsoncmd);