Remove a cached zonefile.
    Idempotent; returns True if deleted or it didn't exist.
    Returns False on error

def remove_atlas_zonefile_data( zonefile_hash, zonefile_dir ):
    """
    Remove a cached zonefile.
    Idempotent; returns True if deleted or it didn't exist.
    Returns False on error
    """
    if not os.path.exists(zonefile_dir):
        return True

    zonefile_path = atlas_zonefile_path( zonefile_dir, zonefile_hash )
    zonefile_path_legacy = atlas_zonefile_path_legacy( zonefile_dir, zonefile_hash )

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

        try:
            os.unlink(zonefile_path)
        except:
            log.error("Failed to unlink zonefile %s (%s)" % (zonefile_hash, zonefile_path))

    return True