lower version, for example 2.6.8
```properties
dubbo.provider.version=1.0
```

2.7.6 failed to recognize the provider url with 'default.version=1.0' key,  it only takes 'version.1.0' into consideration.

Map<String, Map<String, String>> newRegister = UrlUtils.revertRegister(register);
        Map<String, Map<String, String>> expectedRegister = new HashMap<String, Map<String, String>>();
        service.put("dubbo://127.0.0.1:20880/com.xxx.XxxService", null);
        expectedRegister.put("dubbo.test.api.HelloService", service);
        assertEquals(expectedRegister, newRegister);
    }
    @Test
    public void testRevertSubscribe() {
        String key = "perf/dubbo.test.api.HelloService:1.0.0";
        Map<String, String> subscribe = new HashMap<String, String>();
        subscribe.put(key, null);
        Map<String, String> newSubscribe = UrlUtils.revertSubscribe(subscribe);
        Map<String, String> expectSubscribe = new HashMap<String, String>();
        expectSubscribe.put("dubbo.test.api.HelloService", "group=perf&version=1.0.0");
        assertEquals(expectSubscribe, newSubscribe);
    }
    @Test
    public void testRevertSubscribe2() {
        String key = "dubbo.test.api.HelloService";
        Map<String, String> subscribe = new HashMap<String, String>();
        subscribe.put(key, null);
        Map<String, String> newSubscribe = UrlUtils.revertSubscribe(subscribe);
        assertEquals(subscribe, newSubscribe);
    }
    @Test
    public void testRevertNotify() {
        String key = "dubbo.test.api.HelloService";
        Map<String, Map<String, String>> notify = new HashMap<String, Map<String, String>>();
        Map<String, String> service = new HashMap<String, String>();
        service.put("dubbo://127.0.0.1:20880/com.xxx.XxxService", "group=perf&version=1.0.0");