MariaRocks port: fix rocksdb.handler_basic test

MySQL has each storage engine to increment Handler_XXX counters,
while MariaDB has handler::ha_XXX() methods to do the increments.

MariaDB's solution doesn't work for storage engines that implement
handler::read_range_first(), though.
Make ha_rocksdb::read_range_first increment the counter (when it is
calling handler::ha_XXX() function that will)

sql/handler.h

@@ -3928,10 +3928,16 @@ private:
   void mark_trx_read_write_internal();
   bool check_table_binlog_row_based_internal(bool binlog_row);
 
-  /* Private helpers */
+protected:
+  /*
+    These are intended to be used only by handler::ha_xxxx() functions
+    However, engines that implement read_range_XXX() (like MariaRocks)
+    or embed other engines (like ha_partition) may need to call these also
+  */
   inline void increment_statistics(ulong SSV::*offset) const;
   inline void decrement_statistics(ulong SSV::*offset) const;
 
+private:
   /*
     Low-level primitives for storage engines.  These should be
     overridden by the storage engine class. To call these methods, use

storage/rocksdb/ha_rocksdb.cc

@@ -6265,6 +6265,7 @@ int ha_rocksdb::read_range_first(const key_range *start_key,
       DBUG_RETURN(HA_ERR_LOCK_DEADLOCK);
     }
 #endif
+    increment_statistics(&SSV::ha_read_key_count);
 
     MYSQL_TABLE_IO_WAIT(m_psi, PSI_TABLE_FETCH_ROW, active_index, 0,
       { result= index_read_map_impl(table->record[0],