Exercise some care before sending SIGHUP to mountd.

[kib]

Summary

Do trivial checks for the mountd' pid validity before.

[emaste]

Could we (also) add assertions in pidfile_open for this case?

sbin/mount/mount.c

243–244 ↗

(On Diff #55945)

This comment is historically correct, but really we should stop having such bugs - in any case, we don't expect to have more and the comment suggests it's just something that happens occasionally and we're powerless to stop.

I would probably say "has happened due to ..."

[kib]

Update comment.