Fix incorrect detection of a cloudlinux kernel as an openvzve

CloudLinux is a patched linux kernel with advanced isolation capabilities that AFAIK borrows pieces of OpenVZ but it's not a virtualized environment in any way and the `virtual` grain should therefor be detected as physical.

Without this patch CloudLinux is detected as `openvzve` because the `/proc/vz` dir is present like in a real openvzve but there is no `veinfo` file inside, which could be used as a discriminant factor.