[CentOS-virt] Install of kernel-ml does not allow for usable /proc/xen

Working upstream (https://bugzilla.kernel.org/show_bug.cgi?id=117901 and http://elrepo.org/bugs/view.php?id=648) I need to report that the install of kernel-ml-4.5.3 does not trigger the proper grub2 changes to end up with a xen ready kernel after install with "kernel-ml" as the default kernel in /etc/sysconfig/kernel.

However, if I manually run /usr/bin/grub-bootxen.sh, the grub2 entries are properly modified to allow for xen(xl) to function as the /proc/xen is properly created with the kernel options.

I believe this did properly work for kernel-ml-4.5.0 as I did not need to do anything in order for 4.5.0 to be xen enabled.

Thanks PJWelsh