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.

path = path.substring(1);
        }
        this.path = path;
        if (parameters == null) {
            parameters = new HashMap<>();
        } else {
            parameters = new HashMap<>(parameters);
        }
        this.parameters = Collections.unmodifiableMap(parameters);
        this.methodParameters = Collections.unmodifiableMap(methodParameters);
    }
    private static String getAddress(String host, int port) {
        return port <= 0 ? host : host + ':' + port;
    }
    /**
     * Parse url string
     *
     * @param url URL string
     * @return URL instance
     * @see URL
     */
    public static URL valueOf(String url) {
        if (url == null || (url = url.trim()).length() == 0) {
            throw new IllegalArgumentException("url == null");
        }
        String protocol = null;
        String username = null;
        String password = null;
        String host = null;
        int port = 0;