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}