awful.tooltip: call set_geometry on show()

Function set_geometry was never called if the timer_function argument
was omitted. show function only called place() which would not display
a tooltip since it didn't have proper geometry.

Signed-off-by: Adrian C. (anrxc) <anrxc@sysphere.org>
Signed-off-by: Julien Danjou <julien@danjou.info>

lib/awful/tooltip.lua.in

@@ -97,7 +97,7 @@ local function show(self)
             data[self].timer:start()
         end
     end
-    place(self)
+    set_geometry(self)
     self.wibox.visible = true
     self.visible = true
 end