Stop comparing md5 to know if qemu.conf got changed

This partially reverts 72fb4e7c.

Chef::Util::FileEdit is now fixed so there's no need to do that hack
anymore.
Merge pull request #203 from vuntz/suse-only-no-md5

https://github.com/crowbar/barclamp-nova/pull/203

Merged by devtool for cloudsleuth