submodule update: use die_message()

Use die_message() to print the "fatal: " prefix instead of doing it in
git-submodule.sh and remove a now-unnecessary exit code from "git
submodule--helper run-update-procedure".

Also, since die_message() adds the newline for us, replace an invocation
of die_with_status() with printf + exit invocations that do not add a
newline, but are otherwise identical to die_with_status().

Helped-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Glen Choo <chooglen@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-submodule.sh

@@ -404,7 +404,7 @@ cmd_update()
 		# exit codes for run-update-procedure:
 		# 0: update was successful, say command output
 		# 1: update procedure failed, but should not die
-		# 2 or 128: subcommand died during execution
+		# 128: subcommand died during execution
 		# 3: no update procedure was run
 		res="$?"
 		case $res in
@@ -412,11 +412,12 @@ cmd_update()
 			say "$out"
 			;;
 		1)
-			err="${err};fatal: $out"
+			err="${err};$out"
 			continue
 			;;
-		2|128)
-			die_with_status $res "fatal: $out"
+		128)
+			printf >&2 "$out"
+			exit $res
 			;;
 		esac