patch 8.1.0447: GUI scrollbar test fails with Athena and Motif

Problem:    GUI scrollbar test fails with Athena and Motif.
Solution:   When not using on-the-fly scrolling call normal_cmd().
diff --git a/src/evalfunc.c b/src/evalfunc.c
index dd9bc18..c9f4c45 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -3588,7 +3588,7 @@
 
 		if (!dangerous)
 		    ++ex_normal_busy;
-		exec_normal(TRUE, TRUE);
+		exec_normal(TRUE, FALSE, TRUE);
 		if (!dangerous)
 		    --ex_normal_busy;
 
@@ -13233,6 +13233,10 @@
 	return;
     }
     gui_drag_scrollbar(sb, value, dragging);
+# ifndef USE_ON_FLY_SCROLL
+    // need to loop through normal_cmd() to handle the scroll events
+    exec_normal(FALSE, TRUE, FALSE);
+# endif
 }
 #endif