teuthology-node-cleanup: use same timezone as local

[kshtsk]

Fixes: https://tracker.ceph.com/issues/72773

[zmc]

On main:

>>> now = datetime.datetime.now(datetime.timezone.utc)
>>> now
datetime.datetime(2025, 12, 3, 18, 40, 4, 927253, tzinfo=datetime.timezone.utc)
>>> tzhere = now.astimezone().tzinfo
>>> job_updated = '2025-12-03 18:00:00'
>>> delta = now - parse_timestamp(job_updated)
>>> delta.total_seconds() / 3600
0.6680353480555555

With these changes:

>>> now = datetime.datetime.now(datetime.timezone.utc)
>>> now
datetime.datetime(2025, 12, 3, 18, 39, 28, 578278, tzinfo=datetime.timezone.utc)
>>> tzhere = now.astimezone().tzinfo
>>> job_updated = '2025-12-03 18:00:00'
>>> delta = now - parse_timestamp(job_updated, tzhere)
>>> delta.total_seconds() / 3600
-6.3420615894444445

This would cause significant problems in sepia (where everything is UTC). I suggest we do all calculations using UTC.

[kshtsk]

On main:

>>> now = datetime.datetime.now(datetime.timezone.utc)
>>> now
datetime.datetime(2025, 12, 3, 18, 40, 4, 927253, tzinfo=datetime.timezone.utc)
>>> tzhere = now.astimezone().tzinfo
>>> job_updated = '2025-12-03 18:00:00'
>>> delta = now - parse_timestamp(job_updated)
>>> delta.total_seconds() / 3600
0.6680353480555555

With these changes:

>>> now = datetime.datetime.now(datetime.timezone.utc)
>>> now
datetime.datetime(2025, 12, 3, 18, 39, 28, 578278, tzinfo=datetime.timezone.utc)
>>> tzhere = now.astimezone().tzinfo
>>> job_updated = '2025-12-03 18:00:00'
>>> delta = now - parse_timestamp(job_updated, tzhere)
>>> delta.total_seconds() / 3600
-6.3420615894444445

This would cause significant problems in sepia (where everything is UTC). I suggest we do all calculations using UTC.

I guess you're doing it on your laptop, which is in East Pacific?

Here what I have running on UTC, teuthology.front:

(virtualenv) kyr@teuthology:~/teuthology$ python3
Python 3.10.17 (main, Apr  9 2025, 08:54:15) [GCC 9.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import datetime
>>> from teuthology.util.time import parse_timestamp
>>> job_updated = '2025-12-03 18:00:00'
>>> n = datetime.datetime.now(datetime.timezone.utc)
>>> tzhere = n.astimezone().tzinfo
>>> (n - parse_timestamp(job_updated, tzhere)).total_seconds()/3600
1.3768167161111111
>>> (n - parse_timestamp(job_updated)).total_seconds()/3600
1.3768167161111111