git-submodule.sh - Remove trailing / from URL if found

git-submodule.sh - Remove trailing / from URL if found

git clone does not complain if a trailing '/' is included in the origin
URL, but doing so causes resolution of a submodule's URL relative to the
superproject to fail. Regardless of whether git is changed to remove the
trailing / before recording the URL, we should avoid this issue in
submodule as existing repositories can have this problem.

Signed-off-by: Mark Levedahl <mlevedahl@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>