Execute the command as described by a container image. The value of the label is processed
into a command by:
1. Ensuring the first argument of the command is podman.
2. Substituting any variables with those defined by the environment or otherwise.
If no label exists in the container image, nothing is done.
podman container runlabel LABEL IMAGE extra_args
Signed-off-by: baude <bbaude@redhat.com>
