Clean up cosine bell test

[xylar]

This merge includes some clean up that I noticed in the cosine bell test case while writing the tutorial.

• We want to explicitly give the package path and filename for the config file to be read on init.
• We also want to make sure to call the superclass' version of the configure() method even when it's not strictly necessary.
• We can get rid of some code for translating config options to namelist options that are not actually used.

Checklist

• [x] Testing comment in the PR documents testing used to verify the changes

[xylar]

I will keep this in draft mode while I write the tutorial in case other clean-up is necessary.

[xylar]

@cbegeman, this stuff is pretty trivial so I won't ask for a review.

[xylar]

Testing

I tested this on Chrysalis, using a baseline from 2 days ago. The results aren't BFB, showing roundoff-level differences in tracer1 for the final time on the QU60 and Icos60 meshes only. Not sure why but I don't think it indicates a change caused by this PR.