bug#20791: GuixSD: cryptsetup luksFormat hangs when udevd is running

[Benz Schenk]

Setting up luks encrypted partitions with cryptsetup doesn't work when udevd is 
running.

cryptsetup luksFormat got stuck waiting on some semaphore to turn to zero

According to http://www.saout.de/pipermail/dm-crypt/2013-November/003619.html 
this is a udev issue, so i killed udevd and after that it worked

I assume it's some configuration issue with udev, but I don't really know 
enough about this stuff to pinpoint where exactly the problem lies

I'm using the GuixSD 0.8.2 image, if you need any more information about my 
setup, feel free to ask

Benz