control_plane/attachment_service: make --path optional

[jcsp]

Problem

The --path argument is only used in testing, for compat tests that use a JSON snapshot of state rather than the postgres database. In regular deployments, it should be omitted (currently one has to specify --path "")

Summary of changes

Make --path optional.

Checklist before requesting a review

• I have performed a self-review of my code.
• If it is a core feature, I have added thorough tests.
• Do we need to implement analytics? if so did you add the relevant metrics to the dashboard?
• If this PR requires public announcement, mark it with /release-notes label and add several sentences in this section.

Checklist before merging

• Do not forget to reformat commit message to not include the above checklist

[github-actions]

2376 tests run: 2283 passed, 0 failed, 93 skipped (full report)

---

Flaky tests (2)

Postgres 16

• test_lfc_resize: debug

Postgres 15

• test_gc_cutoff: release

Code coverage (full report)

• functions: 54.6% (11226 of 20569 functions)
• lines: 81.6% (62982 of 77217 lines)

---

_{The comment gets automatically updated with the latest test results
5ddc597 at 2024-01-31T16:21:27.609Z :recycle:}