Incorrect VM count reported in Xen4.9 monitoring code

Not sure if it's a Xen4.9 feature or a bug, but Dom0 also shows up in the list of VMs when doing an "xl vm-list". Xen4.6 and older did not. The VM count reported was incorrect(1 extra because of Domain-0) in Xen 4.9. Added a grep to fix this and is backward compatible.