stack/slapos: version up slapos.buildout 2.5.2+slapos014

Thanks to this 'None' is used in BuildoutSerializer

stack/slapos.cfg

@@ -100,7 +100,7 @@ eggs =
 [versions]
 setuptools = 40.4.3
 # Use SlapOS patched zc.buildout
-zc.buildout = 2.5.2+slapos013
+zc.buildout = 2.5.2+slapos014
 # Use SlapOS patched zc.recipe.egg (zc.recipe.egg 2.x is for Buildout 2)
 zc.recipe.egg = 2.0.3+slapos003
 # Use own version of h.r.download to be able to open .xz and .lz archives