Report KCM as unhealthy if leader election is wedged.

Feedback from lavalamp and deads2k.
Changed Check() logic to be central to LeaderElector.
Further changes, especially cleaning up the test code.

Kubernetes-commit: 9c43ee6d6ec6a159b960381af906c130027bc716

tools/leaderelection/leaderelection_test.go

@@ -26,6 +26,7 @@ import (
 	"k8s.io/apimachinery/pkg/api/errors"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/util/clock"
 	fakecorev1 "k8s.io/client-go/kubernetes/typed/core/v1/fake"
 	core "k8s.io/client-go/testing"
 	rl "k8s.io/client-go/tools/leaderelection/resourcelock"
@@ -257,6 +258,7 @@ func testTryAcquireOrRenew(t *testing.T, objectType string) {
 			config:         lec,
 			observedRecord: test.observedRecord,
 			observedTime:   test.observedTime,
+			clock:          clock.RealClock{},
 		}
 
 		if test.expectSuccess != le.tryAcquireOrRenew() {