submodule update --init: correct path handling in recursive submodules

submodule update --init: correct path handling in recursive submodules

When calling `git submodule init` from a recursive instance of
`git submodule update --recursive`, the reported path is wrong as it
skips the nested submodules.

The new test demonstrates a failure in the code prior to this patch.
Instead of getting the expected
    Submodule 'submodule' (${pwd}/submodule) registered for path '../super/submodule'
the `super` directory is omitted and you get
    Submodule 'submodule' (${pwd}/submodule) registered for path '../submodule'
instead.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>