Fix bug in dep tree when modifier deps are modified wavelengths

[djhoese]

This PR fixes a bug I encountered when trying to add rayleigh correction to the ABI natural composite. The default rayleigh corrector/modifier in visir.yaml depends on a sunz_corrected 0.67 band. This is C02 for ABI. C02 is also needed to make the natural RGB and is specified by name.

Before this PR these dependencies would show up in the dependency tree as two separate nodes. One as the 0.67 modified key, one as the C02 modified key. From what I can tell this happens because when the dep tree checks if C02 is in the dep tree it thinks it isn't there, but it is actually there as the 0.67 dependency. The key for the 0.67 dependency is never "filled in" with the details of it's unmodified dataset (name, resolution, calibration, etc). This PR fixes this. I think I had this behavior implemented in the past but removed it for some reason. Tests pass, so I don't know.

This bug comes up semi-randomly based on the order that dependencies are loaded/processed.

P.S. I thought I'd start making PRs from my own fork instead of the satpy one. Maintainers should still have push permissions to my branch through this PR. This follows how I've seen other projects do it where they only have a master branch instead of a develop/master branch pair.

• Tests added
• Tests passed
• Passes git diff origin/develop **/*py | flake8 --diff

[coveralls]

Coverage increased (+0.1%) to 60.802% when pulling a948947 on davidh-ssec:bugfix-mod-with-wl-dep into 547819c on pytroll:develop.

[coveralls]

Coverage increased (+0.1%) to 60.802% when pulling a948947 on davidh-ssec:bugfix-mod-with-wl-dep into 547819c on pytroll:develop.