`Degraded` mode is set automatically after error counter is over the
threshold. `ReadOnly` mode can still be set by an administrator.
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
Implement `RefillMetabase` method to `shardconfig.Config` type which reads
`refill_metabase` config value. Pass the result to `WithRefillMetabase`
option.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>