Do not use fedora-container-common.ks in fedora-eln-container-base.ks
    
    The Fedora ELN container is special in a way that the "%{fedora}"
    RPM macro is not defined there. This breaks the Fedora ELN container
    build, because fedora-container-common.ks expects this macro to exist.
    
    This commit merges fedora-container-common.ks into
    fedora-eln-container-base.ks and hardcodes Fedora 34 GPG key there.
    
    The fedora-eln-container-base.ks will be updated once we move to
    newer Fedora.
    
    Signed-off-by: Jan Kaluza <jkaluza@redhat.com>