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.

this.host = null;
        this.port = 0;
        this.address = null;
        this.path = null;
        this.parameters = null;
        this.methodParameters = null;
    }
    public URL(String protocol, String host, int port) {
        this(protocol, null, null, host, port, null, (Map<String, String>) null);
    }
    public URL(String protocol, String host, int port, String[] pairs) { 
        this(protocol, null, null, host, port, null, CollectionUtils.toStringMap(pairs));
    }
    public URL(String protocol, String host, int port, Map<String, String> parameters) {
        this(protocol, null, null, host, port, null, parameters);
    }
    public URL(String protocol, String host, int port, String path) {
        this(protocol, null, null, host, port, path, (Map<String, String>) null);
    }
    public URL(String protocol, String host, int port, String path, String... pairs) {
        this(protocol, null, null, host, port, path, CollectionUtils.toStringMap(pairs));
    }
    public URL(String protocol, String host, int port, String path, Map<String, String> parameters) {
        this(protocol, null, null, host, port, path, parameters);
    }
    public URL(String protocol, String username, String password, String host, int port, String path) {
        this(protocol, username, password, host, port, path, (Map<String, String>) null);
    }
    public URL(String protocol, String username, String password, String host, int port, String path, String... pairs) {
        this(protocol, username, password, host, port, path, CollectionUtils.toStringMap(pairs));