Do we have the cached zonefile?  It's okay if it's a non-standard zonefile.
    if @validate is true, then check that the data in zonefile_dir_path/zonefile.txt matches zonefile_hash

    Return True if so
    Return False if not

def is_zonefile_cached( zonefile_hash, zonefile_dir, validate=False):
    """
    Do we have the cached zonefile?  It's okay if it's a non-standard zonefile.
    if @validate is true, then check that the data in zonefile_dir_path/zonefile.txt matches zonefile_hash

    Return True if so
    Return False if not
    """
    zonefile_path = atlas_zonefile_path(zonefile_dir, zonefile_hash)
    zonefile_path_legacy = atlas_zonefile_path_legacy(zonefile_dir, zonefile_hash)

    res = False
    for zfp in [zonefile_path, zonefile_path_legacy]:
        
        if not os.path.exists(zfp):
            continue

        if validate:
            data = _read_atlas_zonefile(zfp, zonefile_hash)
            if data:
                # yup!
                res = True
                break

        else:
            res = True
            break

    return res