This cr fixes:
* Replaced ``dateutil.tz.tzlocal()`` and ``dateutil.tz.tzutc()`` with
``datetime.timezone`` built-in classes in audit controllers and
continuous audit scheduling.
* Replaced ``dateutil.parser.parse()`` with
``oslo_utils.timeutils.parse_isotime()`` in the zone migration
strategy for parsing datetime strings.
Closes-Bug: #2118404
Change-Id: I6d8a345fa4339a688769b147413dcdf3016bf4a0
Signed-off-by: Chandan Kumar (raukadah) <chkumar@redhat.com>