Remove retain_cm3_bug in interpolator

[thomas-robinson]

Describe the bug The namelist variable retain_cm3_bug should be removed from FMS

To Reproduce retain_cm3_bug=.true. is set by default. Do we still want to keep this?

Expected behavior This should either be the default behavior and the namelist variable should be removed

System Environment

Additional context This is for the AM5 code prune clean up

[mlee03]

retain_cm3_bugs is set to .false. in the xmls (did not check all the xmls though) and is used/found in other model components listed below:

• atmos_phys, particularly in atmos_shared/tracer_driver

• mom6/coupled_AM2_LM3_SIS/CM2G63L/static_input.nml

• mom6/coupled_AM2_LM3_SIS/CM2G63L/input.nml

I'll remove it and test it.

[thomas-robinson]

@mlee03 Have you made progress on this?

[mlee03]

@thomas-robinson, there's another variable in atmos_shared that is also called retain_cm3_bugs. Though the one in atmos_shared is part of a different nml, I assume they're correlated. I was planning on removing it from atmos_shared also and testing it before making the PR to FMS.

[thomas-robinson]

The project set for this is 2022.04, so this would need to be ready in about 2 weeks to make it in. Do you think that's possible? If so, I will leave it. If not, we can change it to a later release.

[rem1776]

@thomas-robinson I added this to the project a while ago, thought I had it removed. This'll go into the next one (2022.05), at least last I checked with @mlee03