[ Reason ]
When an UPS is running a calibration, nut will set its calibration flag,
but that flag was never cleared, this seems to completely break the
state machine.

[ Impact ]
There are two different bug reports with opposite symptoms. In one the
machine was not shutdown even when the UPS was low on battery. On the
other one, the machine was randomly shutdown, causing a DOS

[ Tests ]
It's difficult to reproduce on my UPS at home, it doesn't support
calibration

[ Risks ]
The patch is trivial and already released in testing and unstable for
months.

[ Checklist ]
  [X] *all* changes are documented in the d/changelog
  [X] I reviewed all changes and I approve them
  [X] attach debdiff against the package in (old)stable
  [X] the issue is verified as fixed in unstable

[ Changes ]
The flag is being cleared when the UPS is not in calibration state.