upas/Mail: fix bug where Redraw must be executed twice to have an effect

upas/Mail: fix bug where Redraw must be executed twice to have an effect

In showlist, call bwindata instead of bwinopen in order to use a
pre-existing fd to write to the data file.  This existing fd will
properly honour any address set by a previous write to the addr file.
Specifically, the redraw function sets addr to "," before calling
showlist in order to overwrite the entire contents of the window.