Configure nginx to allow tower to call /websocket/

[acozine]

Closes #4043.

Attempt to fix issue 4043 with nginx config. Very much WIP.

[acozine]

We ran this today, and while it didn't break anything, we're still seeing the errors in the logs about django.request Not Found: /websocket/. That said, it looked like live job updates might be happening - so maybe the log messages are not tightly coupled to the problem . . . I'm going to hold this PR until we have some EEs and can gather more data.

[acozine]

Job updates are still not happening. If you kick off a job, you see the Waiting for updates message as long as you stay on the Jobs page, long after the job has failed (or succeeded). To see the actual output, you have to go back to Jobs and then select the individual job.

[acozine]

@VickieKarasic and @sandbergja and I fixed this today - in addition to this nginx config update, we had to add a config file to Tower. The file is called /etc/tower/conf.d/websocket_config.py and the content is:

# support headers for real-time updates via websocket
BROADCAST_WEBSOCKET_PROTOCOL = 'https'
BROADCAST_WEBSOCKET_PORT = 443
BROADCAST_WEBSOCKET_VERIFY_CERT = True

With those two changes, the WebSockets connections works and live updates come through. If you inspect the web browser, there are still some errors listed, but they don't seem to affect performance, so we are ignoring them for now.

[kayiwa]

NICE! thanks @acozine