CI: Azure: Move to Ubuntu 22.04 image

As per https://github.com/actions/runner-images/issues/6002

 the Ubuntu
18.04 image is deprecated and will be removed by December 1, 2022.
Move to the Ubuntu 22.04 image as our base for launching our containers
from.

Signed-off-by: Tom Rini <trini@konsulko.com>