systemd: disable python

* otherwise configure uses python-config from host and passes wrong CFLAGS
  see http://lists.linuxtogo.org/pipermail/openembedded-devel/2012-October/042058.html


  for details

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>