Adds support of DATM_MODE=CLM1PT for ELM

[bishtgautam]

Modifications to support user-defined atmospheric forcing
with ELM.

Test suite:
Test baseline:
Test namelist changes:
Test status: [bit for bit, roundoff, climate changing]

Fixes [CIME Github issue #]

User interface changes?:

Update gh-pages html (Y/N)?:

Code review:

[bishtgautam]

The new code in src/components/data_comps_mct/datm/cime_config/buildnml may not be an ideal solution, but I wanted to open this PR to get the conversation started on how to best accommodate these changes.

[jedwards4b]

I don't see any problems with this.

[bishtgautam]

It seems I broke a test.

[jedwards4b]

You did - do you know where to find the log? I also notice that you didn't run scripts_regression_tests.py locally for this PR. Can you please do that and update the initial comment of the conversation.

======================================================================
FAIL: test_pylint_src_components_data_comps_mct_datm_cime_config_buildnml (__main__.B_CheckCode)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "./scripts_regression_tests.py", line 3480, in test
    self.assertTrue(result == "", msg=result)
AssertionError: False is not true : ************* Module buildnml
W: 57, 0: Bad indentation. Found 13 spaces, expected 12 (bad-indentation)
W: 59, 0: Bad indentation. Found 13 spaces, expected 12 (bad-indentation)
W: 65, 0: Bad indentation. Found 13 spaces, expected 12 (bad-indentation)
W: 67, 0: Bad indentation. Found 13 spaces, expected 12 (bad-indentation)

[jgfouca]

The code looks identical in both branches with the only difference being ELM vs CLM. You should capture this difference in a single string so the code can be reused.

[jedwards4b]

Better, thanks.

[rljacob]

@jgfouca this should be merged if you're happy with it.