option to wait for pid file to appear

[J.deBoynePollard-newsgroups@xxxxxxxxxxxx (Jonathan de Boyne Pollard)]

Mantas MikulÄ?nas:
> Maybe socket-activation would work for you? (With Nginx it's also a 
> hack though.)

Accept=No
Environment=NGINX=3;

It is not terrifically complex.  The documented way to stop the forking 
is "daemon off", but an inherited listening socket also does it.

* https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=728015

* 
https://github.com/nginx/nginx/blob/8e8734ec82cde91a02d0cbfaae0d0df6b5aaab14/src/core/nginx.c#L347