fix: controller test 201 and fix test clean-up

```
❯ go test ./controllers -parallel=1 -count=3 -test.run="Test_000201"
ok      github.com/weaveworks/tf-controller/controllers 99.224s
```

For the cleanup:
Sadly `resource.GetObjectKind().GroupVersionKind().Kind` is an empty
string, so it didn't work at all.

Fixes #947

References:
* #947

Signed-off-by: Balazs Nadasdi <balazs@weave.works>

controllers/cleaner_test.go

@@ -29,7 +29,7 @@ func waitResourceToBeDelete(g gomega.Gomega, resource client.Object) {
  return k8sClient.Get(ctx, key, resource)
  }, cleanupTimeoutSeconds, interval).ShouldNot(gomega.Succeed())
 
- if resource.GetObjectKind().GroupVersionKind().Kind == infrav1.TerraformKind {
+ if _, ok := resource.(*infrav1.Terraform); ok {
  waitDefaultSecretsToBeDeletedForTerraform(g, resource)
  }
 }

controllers/tc000201_auto_approve_with_disabled_drift_detection_test.go

@@ -1,5 +1,3 @@
-//go:build flaky
-
 package controllers
 
 import (
@@ -44,7 +42,7 @@ func Test_000201_auto_approve_with_disabled_drift_detection(t *testing.T) {
  },
  }
  g.Expect(k8sClient.Create(ctx, &testRepo)).Should(Succeed())
- defer func() { g.Expect(k8sClient.Delete(ctx, &testRepo)).Should(Succeed()) }()
+ defer waitResourceToBeDelete(g, &testRepo)
 
  By("setting the git repo status object, the URL, and the correct checksum")
  testRepo.Status = sourcev1.GitRepositoryStatus{
@@ -101,7 +99,7 @@ func Test_000201_auto_approve_with_disabled_drift_detection(t *testing.T) {
  },
  }
  g.Expect(k8sClient.Create(ctx, &helloWorldTF)).Should(Succeed())
- defer func() { g.Expect(k8sClient.Delete(ctx, &helloWorldTF)).Should(Succeed()) }()
+ defer waitResourceToBeDelete(g, &helloWorldTF)
 
  By("checking that the hello world TF gets created")
  helloWorldTFKey := types.NamespacedName{Namespace: "flux-system", Name: terraformName}