message: fix process::signal error
diff: @@ -711,6 +711,15 @@ int php_swoole_process_start(swWorker *process, zval *zobject)
  }
  swSignal_clear();
  + int i;
  + for(i=0; i<SW_SIGNO_MAX; i++)
  + {
  + if (signal_callback[i])
  + {
  + sw_zval_free(signal_callback[i]);
  + signal_callback[i] = NULL;
  + }
  + }
  zend_update_property_long(swoole_process_class_entry_ptr, zobject, ZEND_STRL("pid"), process->pid);
  zend_update_property_long(swoole_process_class_entry_ptr, zobject, ZEND_STRL("pipe"), process->pipe_worker);
  