Count the work the take-ins start in the background, so a test's mesh closes only once that work has ended (issue 1851, A5-A7; issue 1790, D3)

cmd/mesh-controller/mesh_for_test.go

@@ -56,6 +56,8 @@ func aMeshOnTheStore(t *testing.T) *stores {
 		t.Fatal(err)
 	}
 	t.Cleanup(open.Close)
+	// The work this mesh started in the background ends before its stores close (cleanups run last first).
+	t.Cleanup(background.Wait)
 	// A condition store of its own, held in memory (novox/hq to-be 45 §2): status leads with what is
 	// open, and a mesh with no bus would otherwise read as one whose conditions cannot be read.
 	withConditionsInMemory(t)