folder_branch_ops: don't cache block before it hits the server
folder_branch_ops: don't cache block before it hits the server

Just let finalizeBlocksLocked() deal with putting blocks in the cache.

Issue: #392

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