herbstluftwm: kill all instances of panel.sh on restart

.config/herbstluftwm/autostart

@@ -212,6 +212,7 @@ hc set focus_follows_mouse 1
 
 # panel
 hc detect_monitors
+ps aux | grep panel.sh | grep -v grep | awk '{print $2}' | xargs kill
 panel=~/.config/herbstluftwm/panel/panel.sh
 for monitor in $(hc list_monitors | cut -d: -f1); do
     "$panel" "$monitor" &