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.

public URL getUrlParameter(String key) {
        URL u = getUrls().get(key);
        if (u != null) {
            return u;
        }
        String value = getParameterAndDecoded(key);
        if (StringUtils.isEmpty(value)) {
            return null;
        }
        u = URL.valueOf(value);
        getUrls().put(key, u);
        return u;
    }
    public double getParameter(String key, double defaultValue) {
        Number n = getNumbers().get(key);
        if (n != null) {
            return n.doubleValue();
        }
        String value = getParameter(key);
        if (StringUtils.isEmpty(value)) {
            return defaultValue;
        }
        double d = Double.parseDouble(value);
        getNumbers().put(key, d);
        return d;
    }
    public float getParameter(String key, float defaultValue) {
        Number n = getNumbers().get(key);
        if (n != null) {
            return n.floatValue();