Doris support AGG_KEYS/UNIQUE_KEYS/DUP_KEYS/ three storage model.
Among these three model, UNIQUE_KYES/DUP_KEYS is added after AGG_KEYS.
For historical tablet, the keys_type field to indicate storage model
may be missed for AGG_KEYS.
So upgrade from historical tablet, this situation should be taken into
consideration and set to be AGG_KEYS.