Clean expired tokens from the master

def clean_expired_tokens(opts):
    '''
    Clean expired tokens from the master
    '''
    loadauth = salt.auth.LoadAuth(opts)
    for tok in loadauth.list_tokens():
        token_data = loadauth.get_tok(tok)
        if 'expire' not in token_data or token_data.get('expire', 0) < time.time():
            loadauth.rm_token(tok)