ANd that's a wrap for bnc #887801

- Use the x86-64-xen or i386-xen format for the grub2 image creation on EC2
  + this is a follow up change for b1be72f59f5f4498 addressing bnc #887801
    we avoid the hacky symlink introduced by the previous commit.
    This change requires a grub release that contains
    http://git.savannah.gnu.org/cgit/grub.git/commit/ChangeLog?id=9612ebc0