Allow to return chain_info in response to reads

src/osd/osd_primary.h

@@ -56,6 +56,7 @@ struct osd_primary_op_data_t
             int chain_size;
             osd_chain_read_t *chain_reads;
             int chain_read_count;
+            uint8_t *chain_info;
         };
     };
 };