[libvirt] [PATCH] Don't fail lxc domain start when memory controller support is missing

Hi, starting of lxc domains currently fails if memory controller support is disabled in the kernel. Attached patch fixes this by ignoring the error in case the files don't exist in the cgroup filesystem. I didn't add the same exceptions for the recent hard and soft limit code since if somebody sets this values he probably wants them enforced. O.k. to apply? Cheers, -- Guido