layoutbox: Revert 25f4f24791

Apparently, there is such thing as not leaking enough...

Also try to clear the widgets from mywibox. This seem to help.

Time will tell.

Fixes #914, unfixes #808

lib/awful/widget/layoutbox.lua

@@ -56,10 +56,10 @@ function layoutbox.new(screen)
     local w = boxes[screen]
     if not w then
         w = imagebox()
-        w._layoutbox_tooltip = tooltip({ objects = {w}, delay_show = 1 })
+        w._layoutbox_tooltip = tooltip {objects = {w}, delay_show = 1}
 
         update(w, screen)
-        boxes[screen] = setmetatable({}, {__index = w, __newindex = w})
+        boxes[screen] = w
     end
 
     return w

tests/test-leaks.lua

@@ -14,6 +14,7 @@ end
 -- Make the layoutbox in the default config GC'able
 -- luacheck: globals mywibox mylayoutbox
 for s in screen do
+    mywibox[s]:set_widget(wibox.widget.textbox())
     mywibox[s].visible = false
 end
 mywibox = nil