In bce3bd9031, we added support for podman
for building and running the SDK container. The presence of podman is
auto-detected in sdk_container_common.sh. However, podman is preverred
over docker, requiring users to use *sudo* (which podman requires and
docker does not).
This change uses docker when present, podman otherwise. It also improves
podman detection - 'podman' uses argv[0] in its version string, so if
'docker' is a symlink to 'podman', 'podman --version' output uses
'docker'. This broke the SDK container on hosts which have a 'docker'
symlink to 'podman' since 'podman' is then run w/o 'sudo'.
Signed-off-by: Thilo Fromm <thilo@kinvolk.io>
43e8730ffe