This test was trying to test the mechanism to release kernel FDs as needed
to get us under the max_safe_fds limit in case of spill files.  To do that,
it needs to set max_files_per_process to a very low value which doesn't
even permit starting of the server in the case when there are a few already
opened files.  This test also won't work on platforms where we use one FD
per semaphore.

Backpatch-through: 10, till where this test was added
Discussion:
https://postgr.es/m/CAA4eK1LHhERi06Q+MmP9qBXBBboi+7WV3910J0aUgz71LcnKAw@mail.gmail.com
https://postgr.es/m/6485.1578583522@sss.pgh.pa.us