patch 8.2.0907: when using :global clipboard isn't set correctly

Problem:    When using :global clipboard isn't set correctly.
Solution:   Set "clip_unnamed_saved" instead of "clip_unnamed". (Christian
            Brabandt, closes #6203, closes #6198)
diff --git a/src/clipboard.c b/src/clipboard.c
index 7a35112..5db13a0 100644
--- a/src/clipboard.c
+++ b/src/clipboard.c
@@ -1317,7 +1317,12 @@
     }
     if (errmsg == NULL)
     {
-	clip_unnamed = new_unnamed;
+	if (global_busy)
+	    // clip_unnamed will be reset to clip_unnamed_saved
+	    // at end_global_changes
+	    clip_unnamed_saved = new_unnamed;
+	else
+	    clip_unnamed = new_unnamed;
 	clip_autoselect_star = new_autoselect_star;
 	clip_autoselect_plus = new_autoselect_plus;
 	clip_autoselectml = new_autoselectml;