v2api: fix Rename trying to overwrite itself
v2api: fix Rename trying to overwrite itself

We used to do this

  [pid 99182] renameat2(14, "Y_4DAxKvj1QnXmJx2AkrKA", 15, ".", RENAME_NOREPLACE <unfinished ...>

which was not the intention.

rfjakob/gocryptfs,rfjakob/gocryptfs,rfjakob/gocryptfs,rfjakob/gocryptfs