test: pytestify and cleanup test_cc_mounts.py

[TheRealFalcon]

Proposed Commit Message

test: pytestify and cleanup test_cc_mounts.py

Remove `unittest` constructs and remove base classes

Additional Context

I did a bit more refactoring on the first test to make it feel more pytest-native, but functionally all tests should still be the same.

Test Steps

Merge type

• [x] Squash merge using "Proposed Commit Message"
• [ ] Rebase and merge unique commits. Requires commit messages per-commit each referencing the pull request number (#<PR_NUM>)