[RFE] allow custom environmental variables to be passed to containers/hosts

[satelliteqe]

[RFE] allow custom environmental variables to be passed to containers/hosts

[rplevka]

One of the ideas of @JacobCallahan on how to approach this was to update the _sanitize_create_args method to pass any non-recognized docker/podman run keyword args as env vars to the target container rather than stripping them off

[rplevka]

so the env vars seem to be already supported by the underlaying lib, here's a snippet of a nick yaml that sets LOKI_URL var:

  rhel8_docker_promtail:
    container_host: "ubi8:rplevka"
    environment:
      LOKI_URL: "http://foo.bar/baz"

Alternatively, a list of strings can be used:

  rhel8_docker_promtail:
    container_host: "ubi8:rplevka"
    environment:
      - "LOKI_URL=http://foo.bar/baz"