rhel-9.5: revert systemd boot time

[ppisar]

This revers rhel-9.5 commits:

486e9d4
a0ac871
74de8fe
Resolves: https://issues.redhat.com/browse/RHEL-39775

because it causes a regression.

@evan-goode, could you review this revert?

[evan-goode]

I would prefer to keep in the documentation changes (commits "Needs-restarting: punctuation edits" and "Document needs-restarting boot time") but with the systemd method removed:

.. note::
   Needs-restarting will try to guess the boot time using two different methods:

   ``st_mtime of /proc/1``
        Reflects the time the first process was run after booting.
        This works for all known cases except machines without
        a RTC—they awake at the start of the epoch.
   ``/proc/uptime``
        Seconds field of ``/proc/uptime`` subtracted from the current time.
        Works for machines without RTC if the current time is reasonably correct.
        Does not work on containers which share their kernel with the
        host—there, the host kernel uptime is returned.


.. warning::
    Some systems are configured to read the RTC time in the local time
    zone. This mode cannot be fully supported. It will create various problems
    with time zone changes and daylight saving time adjustments. The RTC time
    is never updated, it relies on external facilities to maintain it. **If at
    all possible, use RTC in UTC by calling** ``timedatectl set-local-rtc 0``.
    See ``man timedatectl`` for more information.

The warning about RTC-in-local-TZ is good to have in there.

[ppisar]

I did a partial revert like that in rhel-10. I can post it in a separate pull request for master branch if you want it in master.

But this full revert is for RHEL-9.5. We cannot just enhance the documentation because that would not fulfill approved acceptance criteria.

[evan-goode]

I did a partial revert like that in rhel-10. I can post it in a separate pull request for master branch if you want it in master.

That would be great, thanks.

But this full revert is for RHEL-9.5. We cannot just enhance the documentation because that would not fulfill approved acceptance criteria.

Understood.

[ppisar]

I did a partial revert like that in rhel-10. I can post it in a separate pull request for master branch if you want it in master.

That would be great, thanks.

#538