Fix the bug introduced with the push of the fix for bug#18326: Do not

lock table for writing during prepare of statement.

When single call open_normal_and_derived_tables() was used, we never
set table_count to the right value.  This patch reverts the part of
the old code that does open_tables() (and sets table_count), then
checks if table_list->multitable_view is set (and returns if so, using
table_count value), and only then it does mysql_handle_derived().

sql/sql_prepare.cc

@@ -1142,7 +1142,7 @@ static int mysql_test_update(Prepared_statement *stmt,
   DBUG_ENTER("mysql_test_update");
 
   if (update_precheck(thd, table_list) ||
-      open_normal_and_derived_tables(thd, table_list, 0))
+      open_tables(thd, &table_list, &table_count, 0))
     goto error;
 
   if (table_list->multitable_view)
@@ -1155,6 +1155,13 @@ static int mysql_test_update(Prepared_statement *stmt,
     DBUG_RETURN(2);
   }
 
+  /*
+    thd->fill_derived_tables() is false here for sure (because it is
+    preparation of PS, so we even do not check it).
+  */
+  if (mysql_handle_derived(thd->lex, &mysql_derived_prepare))
+    goto error;
+
 #ifndef NO_EMBEDDED_ACCESS_CHECKS
   /* TABLE_LIST contain right privilages request */
   want_privilege= table_list->grant.want_privilege;