kubeadm: use correct expected key when checking test results

Resulting key needs to be compared with the expected key which
was set for the test case, not just a key.

cmd/kubeadm/app/phases/certs/certs_test.go

@@ -364,7 +364,7 @@ func TestWriteKeyFilesIfNotExist(t *testing.T) {
 		}
 
 		//TODO: check if there is a better method to compare keys
-		if resultingKey.D == key.D {
+		if resultingKey.D == test.expectedKey.D {
 			t.Error("created key does not match expected key")
 		}
 	}