sztp: Support running tests on Fedora with podman

[seroyer]

Fixes #138

• Proper SELinux support for volume mounts
• Do not use nested docker-compose run, see #138
• Do not use ${PWD} in compose file, breaks on Fedora with podman

Signed-off-by: Steven Royer sroyer@redhat.com

[glimchb]

thank you @seroyer for fixing this issue