AMT graceful power operations not supported

[Stefan Helmert]

MAAS switches off computers graceless. Since Intel Haswell AMT supports graceful power operations. MAAS should send a graceful powerdown command to switch off the computer. It should use acpi shutdown. It should also fallback if graceful powerdown times out or an older AMT version is detected. It should also warn after detecting AMT version: "This AMT version is too old for graceful powerdown. Minimum version AMT 9.0 is required for graceful shutdown."

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: maas 2.4.2-7034-g2f5deb8b8-0ubuntu1
ProcVersionSignature: Ubuntu 4.18.0-17.18~18.04.1-generic 4.18.20
Uname: Linux 4.18.0-17-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.6
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Sun Apr 14 13:58:50 2019
InstallationDate: Installed on 2019-04-06 (8 days ago)
InstallationMedia: Ubuntu 18.04.2 LTS "Bionic Beaver" - Release amd64 (20190210)
PackageArchitecture: all
SourcePackage: maas
UpgradeStatus: No upgrade log present (probably fresh install)