awful.wibox.align() in 3.4.x gets the available screen area from
capi.screen[screen].geometry.
this can easily result in overlapping wiboxes since the work area
provided does not account for existing wiboxes.
In my configuration I use a vertical wibox positioned at the
right and it half-overlaps my top wibox because it is streched and
hard-coded to align at the middle.
Signed-off-by: Julien Danjou <julien@danjou.info>