This installs podman inside the nodepool container, which is used by
the dependent change in DIB to extract initial chroot environments
from upstream containers. This eliminates the need to run non-native
tools on build hosts (rpm/zypper on Ubuntu, etc.).
As noted in the config, podman defaults to assuming systemd is
installed and using various systemd interfaces.
Additionally, we map the a volume into the container which allows
nested podman to do what it needs to do.
Needed-By: https://review.opendev.org/700083
Change-Id: I6722aa2b32db57e099dae4417955a8a2cd28847e
a07bb0a0ae