rht_pair_update_type returns the update type of an key-value pair entry.

Currently, this can only be RHT_UPDATE_PUT or RHT_UPDATE_DEL, which correspond, respectively, to an entry placed in the table by rht_put or rht_del.

Note, the RHT_UPDATE_DEL type can only occur for special delete entries left in the dictionary when RHT_INTERSECT semantics are being used.