Refuse a glob as a unit, and make wanted-by say only what it saw

systemctl expands *, ? and [ in a unit argument, so reset-failed or stop
of "*" would have acted on every unit. wanted-by called a link dangling on
any stat error, followed a linked .wants anywhere, and missed most of the
manager's load path; it now says each of these, and says nothing names a
unit only of the directories it searched.

modules/systemd/cmd/systemd-tools/client_test.go

@@ -139,7 +139,7 @@ func TestASystemActEscalatesAndAnswersTheStateAfter(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	if got := append([]string{calls[0].cmd}, calls[0].args...); !reflect.DeepEqual(got, []string{"sudo", "-n", "systemctl", "restart", "sshd.service"}) {
+	if got := append([]string{calls[0].cmd}, calls[0].args...); !reflect.DeepEqual(got, []string{"sudo", "-n", "systemctl", "restart", "--", "sshd.service"}) {
 		t.Fatalf("%v", got)
 	}
 	if r["ok"] != true || r["active"] != "active" || r["mesh_declared"] != false || r["note"] != nil {