on_play cause high cpu usage when return not-200-code

[lystormenvoy]

Step:
add on_play http://127.0.0.1/auth stage=start,done args=$pargs; in rtmp setting
add

location /auth {
    return 403;
}

in http setting.
Then use srs bench to pull flv stream from server, u can see the nginx use 100% cpu in top command.