submodule status: use submodule--helper is-active

Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-submodule.sh

@@ -1010,14 +1010,13 @@ cmd_status()
 	do
 		die_if_unmatched "$mode" "$sha1"
 		name=$(git submodule--helper name "$sm_path") || exit
-		url=$(git config submodule."$name".url)
 		displaypath=$(git submodule--helper relative-path "$prefix$sm_path" "$wt_prefix")
 		if test "$stage" = U
 		then
 			say "U$sha1 $displaypath"
 			continue
 		fi
-		if test -z "$url" ||
+		if ! git submodule--helper is-active "$sm_path" ||
 		{
 			! test -d "$sm_path"/.git &&
 			! test -f "$sm_path"/.git