largefiles: avoid printing messages while rebasing by "_lfstatuswriters"
Putting "lambda *msg, **opts: None" (= avoid printing messages always)
into "_lfstatuswriters" while rebasing makes explicit passing
"printmessage = False" for "updatelfiles()" useless.
This patch also removes setting/unsetting "repo._isrebasing" in
"overriderebase", because there is no code path referring it.
{header}
# HG changeset patch
# User {author}
# Date {date|hgdate}
# Node ID {node}
{parent%changesetparent}
{desc}
{diff}