Avoid update hook during git-rebase --interactive

Avoid update hook during git-rebase --interactive

If we are rebasing changes that contain potential whitespace
errors that our .git/hooks/pre-commit hook looks for and fails
on then git-commit will fail to commit that change.  This causes
git-rebase--interactive to squash commits together, even though it
was not requested to do so by the todo file.

Passing --no-verify to git-commit makes git-rebase -i behave more
like git-rebase normally would in such conditions, providing more
consistent behavior between the different rebase implementations.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>