This patch is changing the default bootloader for PXE + UEFI to Grub2.
Prior to this patch Elilo was the default but, Elilo is no longer
maintained with the last release dating 2014.
Ironic should have sane defaults therefore we should not rely on an
unmaintained project.
Change-Id: Ib34fcbd37e4698bf272582c96b1540b511b5a892