block_journal: reorg entry removal code
block_journal: reorg entry removal code

Suggested by @akalin-keybase.

Issue: #473

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