python: Fix logging call

python: Fix logging call

ERROR(<class AttributeError>): uncaught exception - RootLogger object has no attribute notice
  File "/samba/bin/python/samba/netcmd/__init__.py", line 387, in _run
    return self.run(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/samba/bin/python/samba/netcmd/domain/backup.py", line 698, in run
    logger.notice("back-up has no sysvol data")
    ^^^^^^^^^^^^^

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15852

Signed-off-by: Jennifer Sutton <jennifersutton@catalyst.net.nz>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>