patch 8.0.0440: not enough test coverage in Insert mode

Problem:    Not enough test coverage in Insert mode.
Solution:   Add lots of tests.  Add test_override(). (Christian Brabandt,
            closes #1521)
diff --git a/src/edit.c b/src/edit.c
index 6621515..065b030 100644
--- a/src/edit.c
+++ b/src/edit.c
@@ -2262,7 +2262,10 @@
 	    vim_beep(BO_COMPL);
 	    setcursor();
 	    out_flush();
-	    ui_delay(2000L, FALSE);
+#ifdef FEAT_EVAL
+	    if (!get_vim_var_nr(VV_TESTING))
+#endif
+		ui_delay(2000L, FALSE);
 	}
 	return FALSE;
     }