Unit/functional test improvements to enable CTSM SystemTests

[samsrabin]

• Gets actual path to default config file to enable running from anywhere.
• Adds an error check that would have helped in my troubleshooting.
• Adds optional --config-file argument.
• Adds netCDF file required for unit testing.

CTSM PR here: ESCOMP/CTSM#3251

[samsrabin]

@glemieux I've added a netCDF file required by the functional unit testing, via git LFS, which seems new for the FATES repo. I wanted to check in with you on that—does it seem acceptable? This means that any tracked netCDF files will be handled by git LFS, but I left *.nc in the .gitignore file, so actually tracking a netCDF file will require someone to use the --force flag with git add.

[glemieux]

@glemieux I've added a netCDF file required by the functional unit testing, via git LFS, which seems new for the FATES repo. I wanted to check in with you on that—does it seem acceptable? This means that any tracked netCDF files will be handled by git LFS, but I left *.nc in the .gitignore file, so actually tracking a netCDF file will require someone to use the --force flag with git add.

I think that makes sense. I like keeping the .nc file in the .gitignore but allowing a way to force it for testing. Thanks for checking.

[samsrabin]

Thanks! Converting to draft while I work on a SystemTest for run_functional_tests.py.

[samsrabin]

Hmm. git lfs is giving me trouble. Reverted and testing some more.

[samsrabin]

Closing to replace with NGEET#1426.