Set the container environment variable to oci.
    
    Certain applications are using the container env variable to
    know if they are running in a container or not. This is making sure
    we have this define in the fedora base image..
    
    Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1399507
    
    Signed-off-by: Clement Verna <cverna@tutanota.com>