1.Based on this post, do the following:

Login as root on your Xenserver host (dom0):

Edit the file /usr/lib/python2.4/site-packages/grub/GrubConf.py.

        Change line 428 from:

        if arg.strip() == "${saved_entry}":

        into:

        if arg.strip() == "${saved_entry}" or arg.strip() == "${next_entry}":
 

2.Create a new VM template for XenCenter
bash:
TEMPLATE_UUID=xe template-list name-label="Ubuntu Lucid Lynx 10.04 (64-bit)" params=uuid --minimal
NEW_TEMPLATE_UUID=xe vm-clone uuid=$TEMPLATE_UUID new-name-label="Ubuntu Trusty 14.04 (64-bit)"
xe template-param-set other-config:default_template=true other-config:debian-release=trusty uuid=$NEW_TEMPLATE_UUI

3.Create the VM from template using XenCenter
(1)In xenCenter select ubuntu 14.04
(2)”installation media ” select install from URL:
http://us.archive.ubuntu.com/ubuntu