Fix GFS Driver Translate Test

[oelbert]

Describe the bug
The GFS driver translate test fails because the config doesn't specify what physics scheme to use. It should have namelist["schemes"] = "GFS_microphysics" for now, but what is the best way to do this? Should we put a default scheme in the namelist defaults? Modify the namelist in the test data in the meantime?

To Reproduce
Try to run the TranslateGFSPhysicsDriver test

Expected behavior
The test should pass instead of crashing with an AttributeError on 'schemes'

[oelbert]

to be fixed in #10