The willRenameFiles loop caught every non-abort, non-method-not-found
error into serverNotes and fell through to fs.rename, so a genuine
failure from a server that supports the request moved the path without
its semantic edits, leaving references dangling. Split client acquisition
from the request, track hard failures, and abort before any mutation when
a supporting server errors. Servers replying method-not-found are still
skipped without blocking.
Fixes#8380
roboomp
fc37f20dea