Use Fatalf instead of Errorf when mounter/unmounter if nil in volume tests

pkg/volume/host_path/host_path_test.go

@@ -225,7 +225,7 @@ func TestPlugin(t *testing.T) {
 		t.Errorf("Failed to make a new Mounter: %v", err)
 	}
 	if mounter == nil {
-		t.Errorf("Got a nil Mounter")
+		t.Fatalf("Got a nil Mounter")
 	}
 
 	path := mounter.GetPath()
@@ -242,7 +242,7 @@ func TestPlugin(t *testing.T) {
 		t.Errorf("Failed to make a new Unmounter: %v", err)
 	}
 	if unmounter == nil {
-		t.Errorf("Got a nil Unmounter")
+		t.Fatalf("Got a nil Unmounter")
 	}
 
 	if err := unmounter.TearDown(); err != nil {
@@ -288,6 +288,9 @@ func TestPersistentClaimReadOnlyFlag(t *testing.T) {
 	spec := volume.NewSpecFromPersistentVolume(pv, true)
 	pod := &v1.Pod{ObjectMeta: metav1.ObjectMeta{UID: types.UID("poduid")}}
 	mounter, _ := plug.NewMounter(spec, pod, volume.VolumeOptions{})
+	if mounter == nil {
+		t.Fatalf("Got a nil Mounter")
+	}
 
 	if !mounter.GetAttributes().ReadOnly {
 		t.Errorf("Expected true for mounter.IsReadOnly")