[chef] Chef server is ignoring /etc/chef-server/chef-server.rb?

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I'm pretty new to Chef, so maybe I'm missing something obvious.  I'm setting 
up
Chef to manage an MPI cluster on a set of nodes running Ubuntu Linux 12.04.  I
followed the instructions for setting up the open source Chef Server version
11.0.11, and it seems like everything is fine; I've got my head node and 
worker
nodes all working as expected.

However, I'd like to stop Chef's embedded nginx from listening to port 80 on
the Chef server so that I can run a different service on that port.  According
to http://docs.opscode.com/config_rb_chef_server.html , I should be able to
create a file at /etc/chef-server/chef-server.rb containing
"nginx['non_ssl_port'] = nil" and then run "sudo chef-server-ctl reconfigure"
to do so, right?

I've done so, but it didn't seem to have any effect.  nginx is still listening
on port 80, and the output from chef-server-ctl didn't look like it was 
parsing
chef-server.rb or changing anything in the nginx config at all.  I've tried
restarting the Chef server and setting miscellaneous other values in there,
too, but it seems like nothing has any effect.

Am I missing something?  Is there a way to tell where Chef thinks it's loading
its server config from?

Thanks,
P. J. Reed