fix minor code unreachability error (#11040)

Signed-off-by: Abirdcfly <fp544037857@gmail.com>

discovery/marathon/marathon_test.go

@@ -159,10 +159,10 @@ func TestMarathonSDRemoveApp(t *testing.T) {
 	tg2 := tgs[0]
 
 	if tg2.Source != tg1.Source {
-		t.Fatalf("Source is different: %s != %s", tg1.Source, tg2.Source)
 		if len(tg2.Targets) > 0 {
-			t.Fatalf("Got a non-empty target set: %s", tg2.Targets)
+			t.Errorf("Got a non-empty target set: %s", tg2.Targets)
 		}
+		t.Fatalf("Source is different: %s != %s", tg1.Source, tg2.Source)
 	}
 }