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.

class URL implements Serializable {
    private static final long serialVersionUID = -1985165475234910535L;
    private final String protocol;
    private final String username;
    private final String password;
    
    private final String host;
    
    private final int port;
    private final String path;
    private final Map<String, String> parameters;
    private final Map<String, Map<String, String>> methodParameters;
    
    private volatile transient Map<String, Number> numbers;
    private volatile transient Map<String, Map<String, Number>> methodNumbers;
    private volatile transient Map<String, URL> urls;
    private volatile transient String ip;
    private volatile transient String full;
    private volatile transient String identity;
    private volatile transient String parameter;
    private volatile transient String string;
    private transient String serviceKey;
    private transient String address;
    protected URL() {
        this.protocol = null;
        this.username = null;
        this.password = null;