Try to fix kiwibuild_bundle_name_format
    
    The idea here is for global_version to be substituted when the
    config file is read, then the remaining string passed through to
    kiwi for use as a template. I believe this config file is read
    through `kobo.conf.PyConfigParser` and so this should work, as
    it claims to support format strings in this way.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>