cr: don't add two updates when renaming with the same directory
cr: don't add two updates when renaming with the same directory

Otherwise there will be an extra, non-custom update that will wreak
havoc with block accounting later on.

Issue: KBFS-574

keybase/client,keybase/kbfs,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/kbfs,keybase/client,keybase/kbfs,keybase/client,keybase/kbfs,keybase/client,keybase/client