message: fix co::exec bug
diff: @@ -109,6 +109,16 @@ pid_t swoole_coroutine_waitpid(pid_t __pid, int *__stat_loc, int __options)
  }
  wait_task task;
  + task.pid = waitpid(__pid, __stat_loc, __options | WNOHANG);
  + if (task.pid > 0)
  + {
  + return task.pid;
  + }
  + else
  + {
  + task.pid = 0;
  + }
  +
  task.co = Coroutine::get_current_safe();
  waitpid_map[__pid] = &task;
  task.co->yield();
  