bug#53207: 28.0.91; create-lockfiles nil breaks file change detection

[Eli Zaretskii]

> Date: Wed, 12 Jan 2022 09:30:07 -0500
> From: "Jay Berkenbilt" <ejb@ql.org>
> 
> Bottom line: in emacs 27.2, setting create-lockfiles to nil does not change 
> the behavior. In emacs 28.0.91, it does. I also noticed this in 28.0.90 but 
> hadn't had time to figure out how to reproduce it without my customizations.

You seem to assume that create-lockfiles is _only_ about the creation
of the lockfiles.  But that's not true: the variable is a misnomer,
and it actually controls the entire functionality of preventing
editing collisions.  Including the test for the file being modified
behind Emacs's back.  The doc string says:

  Non-nil means use lockfiles to avoid editing collisions.

> Is this change intentional? If so, can I configure something to go
> back to the old behavior?

My suggestion is to stop setting create-lockfiles to a nil value.  Why
is the non-nil value a problem?