fixes required for FATES-E3SM soil coupling restarts

[rgknox]

Description:

This set of changes makes some key fixes to FATES coupling with the hlm's soil. The exponential moving average of NPP is used to drive free-living fixers in those models. Some subtle modifications to how this is calculated and restarted were needed to preserve restart behavior.

Fixes: #1113

Collaborators:

@glemieux

Expectation of Answer Changes:

Free-living fixation is not active in FATES-clm, so until we enable that functionality, there should be no effect. This change specifically will not affect elm coupling, but previous changes related to ema NPP that are now being being brought up to API 29 will result in different results when the models are synchronized.

Checklist

If this is your first time contributing, please read the CONTRIBUTING document.

All checklist items must be checked to enable merging this pull request:

Contributor

• The in-code documentation has been updated with descriptive comments
• The documentation has been assessed to determine if updates are necessary

Integrator

• FATES PASS/FAIL regression tests were run (YES on E3SM, TBD CTSM)
• Evaluation of test results for answer changes was performed and results provided

Documentation

no documentation updates necessary

Test Results:

CTSM (or) E3SM (specify which) test hash-tag:

CTSM (or) E3SM (specify which) baseline hash-tag:

FATES baseline hash-tag:

Test Output:

[rgknox]

fates test suite passes on cheyenne:

> ./cs.status.fails
1103-205239ch_gnu: 5 tests
    FAIL ERS_Lm13.f10_f10_mg37.I2000Clm50Fates.cheyenne_gnu.clm-FatesCold COMPARE_base_rest (EXPECTED FAILURE)
    FAIL PEM_D_Ld15.5x5_amazon.I2000Clm50FatesRs.cheyenne_gnu.clm-FatesColdSeedDisp COMPARE_base_modpes (EXPECTED FAILURE)

 
1103-205239ch_int: 34 tests
    PEND ERP_P72x2_Ld30.f45_f45_mg37.I2000Clm50FatesRs.cheyenne_intel.clm-mimicsFatesCold SHAREDLIB_BUILD (EXPECTED FAILURE)
    FAIL ERS_D_Ld5.1x1_brazil.I2000Clm50FatesCruRsGs.cheyenne_intel.clm-FatesColdHydro COMPARE_base_rest (EXPECTED FAILURE)
    FAIL ERS_Lm12.1x1_brazil.I2000Clm50FatesCruRsGs.cheyenne_intel.clm-FatesFireLightningPopDens COMPARE_base_rest (EXPECTED FAILURE)
    FAIL ERS_Lm13.f45_f45_mg37.I2000Clm50Fates.cheyenne_intel.clm-FatesColdNoComp COMPARE_base_rest (EXPECTED FAILURE)

[glemieux]

fixes #1106