handle NEW/NEW conflicts by being real conflicts

handle NEW/NEW conflicts by being real conflicts

NEW/NEW conflicts could sometime be ignored and replaced by update
metadata instructions

we stop doing this and handle them like any other conflicts

that would cause more download from the server

those conflicts would be solved automatically in case this is not a real
conflict but the client was missing the server reply with the updated
metadata

will enable more changes to improve MOVE detection from server side

Signed-off-by: Matthieu Gallien <matthieu.gallien@nextcloud.com>