Two diff-coverage gaps on the ci-kvm-runner branch:
1. bot_bottle/backend/docker/setup.py: the try/except TimeoutExpired
block added in a prior commit had no tests reaching the subprocess
path. Add two tests to TestDockerSetupStatus: one for the success
path (subprocess returns 0) and one for the TimeoutExpired fallback.
2. bot_bottle/db_store.py: the _connection() context manager change in
is_migrated() was never exercised by unit tests (all callers mock
is_migrated() directly). Add test_db_store.py covering the absent-DB,
missing-schema-table, migrated, and behind-schema cases.
