patch 9.0.0465: cursor moves when cmdwin is closed when 'splitscroll' is off

Problem:    Cursor moves when cmdwin is closed when 'splitscroll' is off.
Solution:   Temporarily set 'splitscroll' when jumping back to the original
            window. (closes #11128)
diff --git a/src/testdir/test_window_cmd.vim b/src/testdir/test_window_cmd.vim
index c9f9caa..872e1ba 100644
--- a/src/testdir/test_window_cmd.vim
+++ b/src/testdir/test_window_cmd.vim
@@ -1734,9 +1734,13 @@
               above copen | wincmd j
               call assert_equal(win_screenpos(0)[0] - tabline, line("w0"))
 
-              " No scroll when opening cmdwin
-              only | norm ggLq:
+              " No scroll when opening cmdwin, and no cursor move when closing
+              " cmdwin.
+              only | norm ggL
+              let curpos = getcurpos()
+              norm q:
               call assert_equal(1, line("w0"))
+              call assert_equal(curpos, getcurpos())
 
               " Scroll when cursor becomes invalid in insert mode
               norm Lic