submodule update: use die_message()

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>