'Applies policy specific updates to the given dict of md5 hashes for
the given ondisk_info.
The only difference between this method and the replication policy
function is the way that data files update hashes dict. Instead of all
filenames hashed into a single hasher, each data file name will fall
into a bucket keyed by its fragment index.
:param hashes: a dict of md5 hashes to be updated
:param ondisk_info: a dict describing the state of ondisk files, as
returned by get_ondisk_files'

def _update_suffix_hashes(self, hashes, ondisk_info):

    for frag_set in ondisk_info['frag_sets'].values():
        for file_info in frag_set:
            fi = file_info['frag_index']
            hashes[fi].update(file_info['timestamp'].internal)
    if ('durable_frag_set' in ondisk_info):
        file_info = ondisk_info['durable_frag_set'][0]
        hashes[None].update((file_info['timestamp'].internal + '.durable'))
