Test fixes

[forsyth2]

Summary

Objectives:

• Make legacy 3.1.0 references consistent with 3.0.0
• Always run land_monthly subtask, as it's needed by e3sm_diags AND ilamb

Issue resolution:

• Resolves issues noted here (incorrect legacy 3.1.0 setup) & here (incorrect activation command for land_monthly)

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]

Another fix to add: don't delete test_campaign output directories at the end of each test. That's causing issues with updating the expected results.
E.g.,:

# assert os.system("rm -r test_campaign_water_cycle_override_output") == 0

EDIT: test_defaults.py could also use this fix.