folder_branch_ops: SyncFromServer shold wait on block archival
folder_branch_ops: SyncFromServer shold wait on block archival

This will be useful for testing.

Issue: KBFS-485

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