[Gluster-Maintainers] Release 5: New option noatime

[Shyam Ranganathan]

Writing this to solicit opinions on merging this [1] change that
introduces an option late in the release cycle.

I went through the code, and most changes are standard option handling
and basic xlator scaffolding, other than the change in posix xlator code
that handles the flag to not set atime and the code in utime xlator that
conditionally sets the flag. (of which IMO the latter is more important
than the former, as posix is just acting on the flag).

The option if enabled would hence not update atime for the following
FOPs, opendir, open, read, and would continue updating atime on the
following FOPs fallocate and zerofill (which also update mtime, so the
AFR self heal on time change would kick in anyways).

As the option suggests, with it enables atime is almost meaningless and
hence it almost does not matter where we update it and where not. Just
considering the problem where atime changes cause AFR to trigger a heal,
and the FOPs above that strictly only change atime handled with this
option, I am looking at this as functionally workable.

So IMO we can accept this even though it is late, but would like to hear
from others if this needs to be deferred till release-6.

Shyam