@param read_op operation to add this action to
@param keys array of pointers to null-terminated keys to get
@param keys_len the number of strings in keys
@param iter where to store the iterator
@param prval where to store the return value from this action
Start iterating over specific key/value pairs
They will be returned sorted by key.
@param read_op operation to add this action to @param keys array of pointers to null-terminated keys to get @param keys_len the number of strings in keys @param iter where to store the iterator @param prval where to store the return value from this action