'Compare the local suffix hashes with the remote suffix hashes
for the given local and remote fragment indexes.  Return those
suffixes which should be synced.
:param local_suff: the local suffix hashes (from _get_hashes)
:param local_index: the local fragment index for the job
:param remote_suff: the remote suffix hashes (from remote
REPLICATE request)
:param remote_index: the remote fragment index for the job
:returns: a list of strings, the suffix dirs to sync'

def get_suffix_delta(self, local_suff, local_index, remote_suff, remote_index):

    suffixes = []
    for (suffix, sub_dict_local) in local_suff.items():
        sub_dict_remote = remote_suff.get(suffix, {})
        if ((sub_dict_local.get(None) != sub_dict_remote.get(None)) or (sub_dict_local.get(local_index) != sub_dict_remote.get(remote_index))):
            suffixes.append(suffix)
    return suffixes
