Kubelet: surface the container creation/start failure reason

Container creation/start failure cannot be reproduced by inspecting the
containers. This change caches such errors so that kubelet can retrieve it
later.

This change also extends FakeDockerClient to support setting error response
for a specific function.

pkg/kubelet/dockertools/docker_test.go

@@ -243,7 +243,7 @@ func TestPull(t *testing.T) {
 func TestDockerKeyringLookupFails(t *testing.T) {
 	fakeKeyring := &credentialprovider.FakeKeyring{}
 	fakeClient := &FakeDockerClient{
-		Err: fmt.Errorf("test error"),
+		Errors: map[string]error{"pull": fmt.Errorf("test error")},
 	}
 
 	dp := dockerPuller{
@@ -394,7 +394,7 @@ func TestIsImagePresent(t *testing.T) {
 }
 
 func TestGetRunningContainers(t *testing.T) {
-	fakeDocker := &FakeDockerClient{}
+	fakeDocker := &FakeDockerClient{Errors: make(map[string]error)}
 	fakeRecorder := &record.FakeRecorder{}
 	containerManager := NewDockerManager(fakeDocker, fakeRecorder, PodInfraContainerImage)
 	tests := []struct {
@@ -478,14 +478,16 @@ func TestGetRunningContainers(t *testing.T) {
 	}
 	for _, test := range tests {
 		fakeDocker.ContainerMap = test.containers
-		fakeDocker.Err = test.err
+		if test.err != nil {
+			fakeDocker.Errors["inspect_container"] = test.err
+		}
 		if results, err := containerManager.GetRunningContainers(test.inputIDs); err == nil {
 			resultIDs := []string{}
 			for _, result := range results {
 				resultIDs = append(resultIDs, result.ID)
 			}
 			if !reflect.DeepEqual(resultIDs, test.expectedIDs) {
-				t.Errorf("expected: %v, saw: %v", test.expectedIDs, resultIDs)
+				t.Errorf("expected: %#v, saw: %#v", test.expectedIDs, resultIDs)
 			}
 			if err != nil {
 				t.Errorf("unexpected error: %v", err)