init: turn on mdv4 by default
init: turn on mdv4 by default

So it will start working once the mdserver turns it on.

Issue: KBFS-2621

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