DM-11614: Reset filter list before running each test

[timj]

Without this, in pytest, when CFHT tests run they define a "u" filter,
and when the DECam tests run they fail because the "u" filter
has already been defined.

[parejkoj]

Although it's probably not a bad idea to do this here, I think the better solution is the one employed in DM-9297, resetting the filters in the obs package, before they are (re)defined. See the discussion when I fixed this for lsstSim here:

https://jira.lsstcorp.org/browse/DM-9297

[timj]

This explains why lsstSim worked and Decam failed. This is blocking the pytest merge and I'm not sure I'm up to speed enough to patch obs_decam.

[parejkoj]

I'd guess that adding afwImageUtils.resetFilters() to decamMapper.py:60 in obs_decam and to megacamMapper.py:57 in obs_cfht should do it.

[timj]

I have made the suggested changes to obs_decam and obs_cfht but I am getting push back from @ctslater who doesn't think there should be any special casing and that the tests should run independently outside of pytest. This can be made to work but means we lose the ability to run pytest on its own. I'd prefer this patch be accepted to the jointcal tests to reset them if we aren't going for the obs_ solution.

[timj]

@parejkoj I've reinstated the fix for the tests. The fix is in all of them for consistency and so as not to rely on the behavior of a particular mapper.

[parejkoj]

I wonder if we shouldn't put the resetFilter calls in setUp instead of setupClass? The latter protects from cross-obs runs, but the former would also protect from within-obs runs, I think.

[timj]

It shouldn't do any harm. I'll try it. I hope that setUpClass can't run and be followed by a test from a different class but now I'm wondering about that...