conflict_resolver: don't unref unflushed blocks
conflict_resolver: don't unref unflushed blocks

They just bloat ops and make it harder for the StateChecker to figure
out when a block should be archived vs. missing from the server.

Issue: KBFS-1912

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