flake: TestProvisionerd/CloseCancelsJob

CI Run: https://github.com/coder/coder/actions/runs/24662921525
Job: test-go-pg-17
Commit: 615be176b82070a729e51852ede41bc6f7151257 (Jakub Domeracki)

Failing test:
- provisionerd TestProvisionerd/CloseCancelsJob

Failure excerpt:
```
=== FAIL: provisionerd TestProvisionerd/CloseCancelsJob (0.00s)
provisionerd_test.go:112:
Error: Received unexpected error:
context canceled
Test: TestProvisionerd/CloseCancelsJob
```

Error analysis:
- The provisionerd shutdown path returns `context canceled` from the dRPC stream while the test expects a clean close.
- The test closes provisionerd during parse/init; the failure indicates a timing race in shutdown/cancel handling.

Root cause classification: Flaky test (shutdown timing/race)

Precise assignment analysis:
- `git log --oneline -10 --follow provisionerd/provisionerd_test.go`
- 60b3fd0 chore!: send modules archive over the proto messages (Steven Masley)
- Most recent meaningful modifier of this test file.

Race/Panic/OOM evidence:
- No `WARNING: DATA RACE`, panic, or OOM indicators found in job logs.

Reproduction:
- `go test ./provisionerd -run TestProvisionerd/CloseCancelsJob -count=1`