With the lazy fetch off inside a store transaction, a source or target the
filer holds only on the remote would read as absent to AtomicRenameEntry
and StreamRenameEntry: a rename with FailIfTargetExists could overwrite it,
and a remote-only source would skip the deferred copy. PrefetchRemoteEntries
runs the fetch for both paths before BeginTransaction, under the path locks.
(cherry picked from commit e61f9718018669ef59768cd5eda25b6466d69597)
james
26d1dce6f7