Fixes https://github.com/benoitc/gunicorn/issues/2784:
```
Traceback (most recent call last):
File "/home/runner/work/galaxy/galaxy/galaxy root/.venv/lib/python3.7/site-packages/gunicorn/arbiter.py", line 589, in spawn_worker
worker.init_process()
File "/home/runner/work/galaxy/galaxy/galaxy root/.venv/lib/python3.7/site-packages/uvicorn/workers.py", line 66, in init_process
super(UvicornWorker, self).init_process()
File "/home/runner/work/galaxy/galaxy/galaxy root/.venv/lib/python3.7/site-packages/gunicorn/workers/base.py", line 116, in init_process
self.log.close_on_exec()
File "/home/runner/work/galaxy/galaxy/galaxy root/.venv/lib/python3.7/site-packages/gunicorn/glogging.py", line 381, in close_on_exec
for log in loggers():
File "/home/runner/work/galaxy/galaxy/galaxy root/.venv/lib/python3.7/site-packages/gunicorn/glogging.py", line 94, in loggers
return [logging.getLogger(name) for name in existing]
File "/home/runner/work/galaxy/galaxy/galaxy root/.venv/lib/python3.7/site-packages/gunicorn/glogging.py", line 94, in <listcomp>
return [logging.getLogger(name) for name in existing]
RuntimeError: dictionary changed size during iteration
```
that is, to close(0) and open /dev/null as fd=0 instead of fd=3.
(Partially) Revert "Ensure fd 0 stdin </dev/null is always inheritable."
This partially reverts commit 7946678f271e25473618929d6f2725c8c375563e.
When gunicorn --daemon daemonizes the process, prior to this change it was
noted that in the general case (without -R / --enable-stdio-inheritance), when fd 0
was replaced with /dev/null, the dup2 copy is skipped, and per PEP 446
"Make newly created file descriptors non-inheritable", the result was a stdio
fd </dev/null which was non-inheritable. As a result, any launched subprocess
did not have an open 0/stdin fd, which can cause problems in some applications.
This change retains the behaviour of opening /dev/null with fd 0, but adds a call
to os.set_inheritable(..) to ensure the fd is inheritable.
The -R branch had different logic but has now been standardised with the general
case. It was previously opening /dev/null as fd 3 and the dup2() copy made it
inheritable as fd 0. This branch now applies the same logic: open as fd 0
(i.e. after close(0)), then set_inheritable. As a result, an extra fd 3 </dev/null
previously left open is no longer left open.
Signed-off-by: Brett Randall <javabrett@gmail.com>
