
this is a followup to Id2bfd1ed552ed566b14f6ac5b222c011ff918bee while adapting playbooks for Ansible 2.4 compatibility, this place was missed, and playbooks tried to install grub to a wrong device. This patch re-uses the "ironic_root_device" fact set during discovery as grub install target. Change-Id: Ibfd885b4702ff86c802a8d184ebb406aae9262b5