Nginx Upstart script (Ubuntu 12.04)

nginx.conf

### Nginx upstart script
### source: http://serverfault.com/a/391737/70451
### /etc/init/nginx.conf

description "nginx http daemon"

start on (filesystem and net-device-up IFACE=lo)
stop on runlevel [!2345]

env DAEMON=/usr/local/sbin/nginx
env PIDFILE=/var/run/nginx.pid

# Needed to allow Nginx to start, however, the wrong PID will be tracked
expect fork

# Test the nginx configuration (Upstart will not proceed if this fails)
pre-start exec $DAEMON -t

# Ensure nginx is shutdown gracefully
# Upstart will be tracking the wrong PID so the following is needed to stop nginx
post-stop exec $DAEMON -s stop

# Start Nginx
exec $DAEMON

Working for me without the post-stop line. CentOS 6.x
"pre-stop exec $DAEMON -s stop" is ok

This helped me troubleshoot the screwy nginx stops on my server. Ubuntu 12.04.4.
The line that worked for me was:
post-stop exec $DAEMON -s quit