cmd/k8s-operator: rename 'l' variables (#17700)

Single letter 'l' variables can eventually become confusing when
they're rendered in some fonts that make them similar to 1 or I.

Updates #cleanup

Signed-off-by: Fernando Serboncini <fserb@tailscale.com>

cmd/k8s-operator/tsrecorder_test.go

@@ -52,7 +52,7 @@ func TestRecorder(t *testing.T) {
 		Client:      fc,
 		tsClient:    tsClient,
 		recorder:    fr,
-		l:           zl.Sugar(),
+		log:         zl.Sugar(),
 		clock:       cl,
 		loginServer: tsLoginServer,
 	}