MDEV-4786 - merge 10.0-monty - 10.0

Fixed main.partition_cache, main.partition_cache_innodb,
main.partition_cache_myisam, main.query_cache failures.

libmysqld/emb_qcache.cc:
  Restore proper method to retrieve warnings number.

libmysqld/emb_qcache.cc

@@ -487,7 +487,7 @@ int emb_load_querycache_result(THD *thd, Querycache_stream *src)
   data->embedded_info->prev_ptr= prev_row;
 return_ok:
   net_send_eof(thd, thd->server_status,
-               thd->get_stmt_da()->statement_warn_count());
+               thd->get_stmt_da()->current_statement_warn_count());
   DBUG_RETURN(0);
 err:
   DBUG_RETURN(1);