Replace docker with podman in s2i usage

[hhorak]

SSIA

[phracek]

@hhorak Do we really need to mention podman in s2i/bin/run script? In case of package podman-docker is installed, then this is not needed. In the rest of all containers, we use docker. Can we close this issue?

[zmiklank]

@hhorak Do we really need to mention podman in s2i/bin/run script? In case of package podman-docker is installed, then this is not needed. In the rest of all containers, we use docker. Can we close this issue?

I know that I am not hhorak, but I think we should indeed use podman in docs or usage information because we use podman internally (except for rhel7, centos7) even thoug we call it with docker alias. Podman, not docker, is also the supported container engine for RHEL releases.

[phracek]

LGTM.

[phracek]

[test]

[zmiklank]

I've rebased this on master so that we can run tests.
[test]

[zmiklank]

And added distgen-generated content.

[test]