interfaces: clarify `crAction.do()` return values
interfaces: clarify `crAction.do()` return values

Suggested by songgao.

Issue: #1769

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