Remove dependency of generated client part 3

Replace generated discovery client with client-go client.
Remove generated client from PVR action.
Remove generated client from pkg/cmd directory.
Delete velero generate client from client factory.

Signed-off-by: Xun Jiang <jxun@vmware.com>

pkg/client/factory_test.go

@@ -112,11 +112,6 @@ func TestFactory(t *testing.T) {
 			assert.Equal(t, test.burst, clientConfig.Burst)
 			strings.Contains(clientConfig.UserAgent, test.baseName)
 
-			client, _ := f.Client()
-			_, e := client.Discovery().ServerGroups()
-			assert.Contains(t, e.Error(), fmt.Sprintf("Get \"%s/api?timeout=", test.expectedHost))
-			assert.NotNil(t, client)
-
 			kubeClient, _ := f.KubeClient()
 			group := kubeClient.NodeV1().RESTClient().APIVersion().Group
 			assert.NotNil(t, kubeClient)