tests: move from lxd -> qemu for autopkgtests

lxd keeps failing with
```
Timed out waiting for container to boot
```
so switch to qemu for a more reliable test env.

.github/workflows/test.yml

@@ -23,13 +23,10 @@ jobs:
     - name: setup
       run: |
         sudo apt-get update
-        sudo apt-get install distro-info autopkgtest git-buildpackage
-        sudo snap install lxd --channel=stable
-        sudo usermod --append --groups lxd $(whoami)
-        sudo lxd init  --auto
-        sudo autopkgtest-build-lxd ubuntu:$(distro-info --stable)
+        sudo apt-get install distro-info autopkgtest git-buildpackage genisoimage
+        sudo autopkgtest-buildvm-ubuntu-cloud -r $(distro-info --stable) -o /tmp
     - name: build source
       run: gbp buildpackage -us -uc -S -d -nc --git-ignore-branch --git-prebuild=
     - name: autopkgtest
       # skipping tests is ok
-      run: autopkgtest -U ../build-area/*.dsc -- lxd autopkgtest/ubuntu/$(distro-info --stable)/amd64 || [ $? == 2 ]
+      run: autopkgtest -U ../build-area/*.dsc -- qemu /tmp/autopkgtest-$(distro-info --stable)-amd64.img || [ $? == 2 ]