[Libguestfs] RHEL 6 guest support

The following patches add RHEL 6 guest support to virt-v2v. This was actually quite a lot easier than I expected. * [PATCH 1/4] Update virt-v2v.conf for RHEL 6 virtio support * [PATCH 2/4] Check kudzu exists before attempting to disable it * [PATCH 3/4] Use dracut rather than mkinitrd if it's available * [PATCH 4/4] Properly convert RHEL 6 guest console