Merge pull request #51130 from luxas/fake_discovery

Automatic merge from submit-queue (batch tested with PRs 51335, 51364, 51130, 48075, 50920)

Add the possibility to set return values for the FakeDiscovery implementation

**What this PR does / why we need it**:

As an user of the fake clientset (with the fake discovery), I want to be able to set the fake server's version on demand like this for example:

```go
func TestFakingServerVersion(t *testing.T) {
	client := fakeclientset.NewSimpleClientset()
	fakeDiscovery, ok := client.Discovery().(*fakediscovery.FakeDiscovery)
	if !ok {
		t.Fatalf("couldn't convert Discovery() to *FakeDiscovery")
	}

	testGitCommit := "v1.0.0"
	fakeDiscovery.FakedServerVersion = &version.Info{
		GitCommit: testGitCommit,
	}

	sv, err := client.Discovery().ServerVersion()
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	if sv.GitCommit != testGitCommit {
		t.Fatalf("unexpected faked discovery return value: %q", sv.GitCommit)
	}
}
```

This PR makes that possible, in wait for a more sophisticated FakeDiscovery implementation generally.

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```
@kubernetes/sig-api-machinery-pr-reviews

pkg/client/clientset_generated/internalclientset/fake/clientset_generated.go

@@ -69,10 +69,9 @@ func NewSimpleClientset(objects ...runtime.Object) *Clientset {
 
 	fakePtr := testing.Fake{}
 	fakePtr.AddReactor("*", "*", testing.ObjectReaction(o))
-
 	fakePtr.AddWatchReactor("*", testing.DefaultWatchReactor(watch.NewFake(), nil))
 
-	return &Clientset{fakePtr}
+	return &Clientset{fakePtr, &fakediscovery.FakeDiscovery{Fake: &fakePtr}}
 }
 
 // Clientset implements clientset.Interface. Meant to be embedded into a
@@ -80,10 +79,11 @@ func NewSimpleClientset(objects ...runtime.Object) *Clientset {
 // you want to test easier.
 type Clientset struct {
 	testing.Fake
+	discovery *fakediscovery.FakeDiscovery
 }
 
 func (c *Clientset) Discovery() discovery.DiscoveryInterface {
-	return &fakediscovery.FakeDiscovery{Fake: &c.Fake}
+	return c.discovery
 }
 
 var _ clientset.Interface = &Clientset{}