Schema 40 adds nodes.parent_lid, backfilled from parent_uid. An upsert
and a new row's stub keep it in step, a folder's new row links the rows
stored before it, and a row merged into a landing folder hands its
children over. A restart places each node under its parent's row as it
is now, so a child whose stored node still names a landed folder's
placeholder lands under the folder's real uid.