Remove PID file at the very end
Remove PID file at the very end

Summary:
> While reproducing the bug from #18517, I've noticed that the bitcoind.pid file has already been removed when the bitcoind hangs.
> This PR makes Shutdown() keep the bitcoind.pid file available until the end.

This is a backport of Core [[https://github.com/bitcoin/bitcoin/pull/18526 | PR18526]]

Test Plan: `ninja all check-all`

Reviewers: #bitcoin_abc, majcosta

Reviewed By: #bitcoin_abc, majcosta

Subscribers: majcosta

Differential Revision: https://reviews.bitcoinabc.org/D8910

Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc