tests: Run apt-i386 scenario with docker

There is a weird bug which breaks apt signature verification in i386
podman containers, e.g. [1]. Run the i386 scenario with docker on GitHub
to work around that.

This works fine on a Fedora 33 host, so this is specific to the podman
backport on GitHub's instances.

[1] https://askubuntu.com/questions/1263284/apt-update-throws-signature-error-in-ubuntu-20-04-container-on-arm/1264921

Author: martinpitt

.github/workflows/tests.yml

@@ -33,5 +33,9 @@ jobs:
           scenario=${scenario%@*}
           script=${scenario%-*}
           release=${scenario#*-}
+
+          # HACK: i386 podman container fails apt signature verification
+          [ "${release#i386}" = "$release" ] || sudo dpkg -P podman
+
           # run as root; current Ubuntu podman breaks user networking ("could not find slirp4netns")
           sudo ${{ matrix.env }} tests/run-${script} $release