tooltip: Pass the parent object to awful.placement, not the position.

By passing the geometry, important information used by
awful.placement.next_to were "lost". Given `next_to` supports both
widget position, the mouse and client/wibox relative positioning, it
has to know the object type.

lib/awful/tooltip.lua

@@ -532,7 +532,7 @@ function tooltip.new(args)
         function self.show(other, geo)
             -- Auto detect clients and wiboxes
             if other.drawable or other.pid then
-                geo = other:geometry()
+                geo = other
             end
 
             -- Cache the geometry in case it is needed later