bpo-35633: test_lockf() fails with "PermissionError: [Errno 13] Permission denied" on AIX (GH-11424)

[bpo-35633](https://bugs.python.org/issue35633): Fix a test regression introduced with [bpo-35189](https://bugs.python.org/issue35189) (PEP 475: fnctl functions are not retried if interrupted (EINTR)).

Not only a blocking IO error needs to be ignored - permission errors also need to be ignored.

p.s. - iirc as a "test" only correction a NEWS item is not required. If this is not correct - just mention, and I'll add a NEWS blurb.


https://bugs.python.org/issue35633