mesh-knowledge tests: set the local zone once before any goroutine, not under a running bus server (race found by the repository check on #237)

inZone wrote time.Local while the bus test's nats server read it from a
goroutine that outlives its test; the race detector the repository check
now runs failed TestAReviewOwedOutlivesARestartAndItsLastTryIsSaid.

modules/mesh-knowledge/cmd/mesh-knowledge/kit_test.go

@@ -40,6 +40,9 @@ func TestMain(m *testing.M) {
 		serve(k, os.Getenv("MESH_KNOWLEDGE_STATUS"))
 		os.Exit(0)
 	}
+	// Every test runs in a zone that is not UTC, so a time said locally is proven to be, wherever the tests run. It
+	// is set once, before any goroutine starts: a test that set it while a bus test's server read it raced.
+	time.Local = testZone
 	code := m.Run()
 	stopPostgres()
 	os.Exit(code)

modules/mesh-knowledge/cmd/mesh-knowledge/review_owed_test.go

@@ -155,13 +155,16 @@ func TestProposedAgainAfterTheLastTryClearsTheNotice(t *testing.T) {
 	})
 }
 
-// inZone sets the local zone to one that is not UTC for one test, so a time said locally is proven to be, wherever
+// testZone is the local zone every test runs in, set once by TestMain: not UTC.
-// the test runs.
+var testZone = time.FixedZone("CEST", 2*60*60)
+
+// inZone says the test needs the local zone not to be UTC; TestMain set it before any goroutine started. Setting it
+// here, under a running bus server's goroutines, was a data race the race detector failed.
 func inZone(t *testing.T) {
 	t.Helper()
-	was := time.Local
+	if time.Local != testZone {
-	time.Local = time.FixedZone("CEST", 2*60*60)
+		t.Fatal("the local zone is not the tests' own: TestMain sets it")
-	t.Cleanup(func() { time.Local = was })
+	}
 }
 
 // novox/hq issue 497: a clear the operator's channel refused keeps its notice as told, and is sent again at the next