Further pcmdi_diags updates

[forsyth2]

Summary

Objectives:

• Follow-up fixes to Add pcmdi #25. Corresponding zppy PR: Further pcmdi_diags updates zppy#742

Select one: This pull request is...

• a bug fix: increment the patch version
• a small improvement: increment the minor version
• a new feature: increment the minor version
• an incompatible (non-backwards compatible) API change: increment the major version

Small Change

• To merge, I will use "Squash and merge". That is, this change should be a single commit.
• Logic: I have visually inspected the entire pull request myself.
• Pre-commit checks: All the pre-commits checks have passed.

[forsyth2]

I have visually inspected these changes, and tested them as part of the testing noted in E3SM-Project/zppy#742 (review).

[forsyth2]

Merging, per the discussion at E3SM-Project/zppy#742 (comment)