check_once_cc_ccache_new_credentials_iterator
check_once_cc_ccache_new_credentials_iterator(ccache, NULL, ccErrBadParam, "NULL out iterator param");
check_once_cc_ccache_new_credentials_iterator(ccache, &creds_iterator, ccErrInvalidCCache, "invalid ccache");
check_once_cc_ccache_new_credentials_iterator(ccache, &creds_iterator, ccNoError, "valid params");
cc_int32 check_once_cc_ccache_new_credentials_iterator(cc_ccache_t ccache, cc_credentials_iterator_t *iterator, cc_int32 expected_err, const char *description);