rebase --update-refs: fix loops

rebase --update-refs: fix loops

The `total_nr` field in the `todo_list` structure merely serves display
purposes, and should only be used when generating the progress message.

In these two instances, however, we want to loop over all of the
commands in the parsed rebase script. The loop limit therefore needs to
be `nr`, which refers to the count of commands in the current
`todo_list`.

This is important because the two numbers, `nr` and `total_nr` can
differ wildly, e.g. due to `total_nr` _not_ counting comments or empty
lines, while `nr` skips any commands that already moved from the
`git-rebase-todo` file to the `done` file.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Acked-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>