Comment 2 for bug 1740824

Reviewed: https://review.openstack.org/489951
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=6f54f5c1e37a42b395ca793f869b73aa902602ed
Submitter: Zuul
Branch: master

commit 6f54f5c1e37a42b395ca793f869b73aa902602ed
Author: Kevin Zhao <email address hidden>
Date: Wed Aug 2 17:50:28 2017 +0800

    Use UEFI as the default boot for AArch64

    There are two ways of booting VM on AArch64 architecture:

    1. UEFI
    2. kernel+initrd

    No one sane goes for 2nd option so hw_firmware_type=uefi has to be set
    for every image. Otherwise they simply hang. So let's set is as default
    if no other value for hw_firmware_type is set.

    If someone will implement own way then they can set hw_firmware_type to
    own value and add support to Nova.

    Closes-Bug: #1740824

    Co-authored-by: Kevin Zhao <email address hidden>
    Change-Id: I70ad5ecb420b7d469854e8743e38ba27fd204747