Merge #14426: utils: Fix broken Windows filelock

Summary:
369244f654 utils: Fix broken Windows filelock (Chun Kuan Lee)

Pull request description:

Fix broken filelock on Windows, also add a test for this. It's a regression introduced by #13862.

Tree-SHA512: 15665b1930cf39ec71f3ab07def8e2897659f6fd4d2de749d63a5a8ec920e4a04282f12bc262f242b1b3d14d2dd9fa191ddbcf16a46fb927b5b2b14d9f6b5d01

Backport Core of PR14426

Test Plan: ninja check check-functional

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D6334