Avoid WorkerProcess._new_stdin FD sharing (#51623) (#51624)
Avoid WorkerProcess._new_stdin FD sharing (#51623) (#51624)

This avoids holding open _new_stdin within the parent process, where
subsequent WorkerProcess forks will duplicate it, producing significant
noise in the FD table of every worker.

Fix by overriding start() and moving the work to there, with a finally:
to ensure parent FD is closed after start().
thaim/ansible,thaim/ansible