Metadata Store Key was changed so that it is not compatible with 2.7.1.

The code is in org.apache.dubbo.metadata.identifier.MetadataIdentifier
@Test
    public void testGetUniqueKey() {
        String interfaceName = "org.apache.dubbo.metadata.integration.InterfaceNameTestService";
        String version = "1.0.0.zk.md";
        String group = null;
        String application = "vic.zk.md";
        MetadataIdentifier providerMetadataIdentifier = new MetadataIdentifier(interfaceName, version, group, PROVIDER_SIDE, application);
        System.out.println(providerMetadataIdentifier.getUniqueKey(MetadataIdentifier.KeyTypeEnum.PATH));
        Assertions.assertEquals(providerMetadataIdentifier.getUniqueKey(MetadataIdentifier.KeyTypeEnum.PATH),
                "metadata" + PATH_SEPARATOR + interfaceName + PATH_SEPARATOR +
                        (version == null ? "" : (version + PATH_SEPARATOR))
                + (group == null ? "" : (group + PATH_SEPARATOR)) + PROVIDER_SIDE
                        + PATH_SEPARATOR + application + PATH_SEPARATOR + "metadata");
        System.out.println(providerMetadataIdentifier.getUniqueKey(MetadataIdentifier.KeyTypeEnum.UNIQUE_KEY));
        Assertions.assertEquals(providerMetadataIdentifier.getUniqueKey(MetadataIdentifier.KeyTypeEnum.UNIQUE_KEY),
                interfaceName + MetadataIdentifier.SEPARATOR +
                        (version == null ? "" : version + MetadataIdentifier.SEPARATOR)
                        + (group == null ? "" : group + MetadataIdentifier.SEPARATOR)
                        + PROVIDER_SIDE + MetadataIdentifier.SEPARATOR + application + META_DATA_STORE_TAG);
    }
}