Minor changes to run 'make iso' on xenial host.
Minor changes to run 'make iso' on xenial host.

- Running chroot without 'sh -c' doesn't set environment variables. This
patch wraps command in 'sh -c'
- add force to mv command as xenial is more strict for changing
  permissions

Change-Id: I83122397c2a8c457abb9687909352179831a46f3
Implements: mos-xenial

stackforge/fuel-main,stackforge/fuel-main,SergK/fuel-main,SergK/fuel-main,SergK/fuel-main,stackforge/fuel-main