Reduce xensource final image to fit in a (4096MB) 4GB partition
Search for the vyos kernel image rather than the old vyatta kernel

When building the xensource image, search for the VyOS kernel image
instead of the Vyatta version.  This is limited to the AMD64 image at
the moment.
Set the domU configuration file to point to xvda and increase memory level

Set the domU configuration file generated to point to xvda instead of
xvda1 for the disk, as a lot lot Xen VPS seem to use whole disks
instead of paritioning.  Also increase the memory level set, as again a
lot of them now give more memory to even smaller systems, so increasing
system performance.
Make sure grub/menu.lst is created correctly and set the root partition

Create the /boot/grub directory so the grub menu.lst configuration file
can be generated correctly, and is then in the expected location for
pygrub/pv-grub to boot from.  Also, update the kernel boot option for
the root partition to point to xvda rather than xvda1.
Update the hostname set in the xensource image from vyatta to vyos
Remove 05-event_tty to prevent T0 from respawning

Remove 05-event_tty from config/chroot_local-hooks for xensource images
to prevent T0 being readded to /etc/inittab for console access, with
the resultant repeated console warning about it respawning to quickly.