i3bar: Fix pixel offset calculation in dual-head

Long description:

When running i3bar on a dual-head display with workspaces enabled in i3bar's
config, the second monitor wouldn't use a correct x position offset and
would draw its label too close to the screen's edge.  In comparison to the
first monitor, this is inconsistent because that starts with a pixel offset
of 1.

To apply this patch, use:
curl http://cr.i3wm.org/patch/163/raw.patch | git am

@@ -1715,7 +1715,7 @@ void draw_bars(bool unhide) {

             unhide = true;

         }

-        i = 0;

+        i = 1;

     }

     if (!mod_pressed) {