app: in Rectangle/Ellipse tools, update selection when clicking inside existing one

In GimpRectangleSelectTool, when creating the rectangle widget as a
result of clicking inside an existing selection, update the
selection at the click, so that the tool's effects are applied
immediately, without having to further modify the selection.

(cherry picked from commit 7d2e872f4f)

app/tools/gimprectangleselecttool.c

@@ -730,9 +730,7 @@ gimp_rectangle_select_tool_commit (GimpRectangleSelectTool *rect_tool)
                                 NULL);
                 }
 
-              gimp_rectangle_select_tool_update_option_defaults (rect_tool,
-                                                                 FALSE);
-              return;
+              gimp_rectangle_select_tool_update (rect_tool);
             }
           else
             {