Try running iot_zezere_server on minimal UEFI image instead
    
    OK, so we can't have parallel tests on different machines, so
    we can't have iot_zezere_server on 64bit and iot_zezere_ignition
    on uefi. We need both to be on uefi. So, let's try using the
    minimal-uefi image that we build for upgrade tests instead. It's
    built for -1 (which is the same as CURRREL) on x86_64 and aarch64
    so it should be there when we need it.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>