nodemap: make sure on disk change get rolled back with the transaction
In case of errors, we need to rollback the change made to the persistent
nodemap.
Differential Revision: https://phab.mercurial-scm.org/D8191
{header}
# HG changeset patch
# User {author}
# Date {date|hgdate}
# Node ID {node}
{parent%changesetparent}
{desc}
{diff}