Fixed double-quoted URL problem in MapAdapter.get_default_redirect

The "default redirecting" feature calls url_quote() twice, which breaks
URLs when they contain non-alphanumeric characters.

I defined the following routing rules:
```python
url_map = Map([
    Rule('/<category>', defaults={'page': 1}, endpoint='category'),
    Rule('/<category>/page/<int:page>', endpoint='category')
])
```

What I expected is:
http://localhost:5000/ham%20egg/page/1
↓(redirection)
http://localhost:5000/ham%20egg

But werkzeug does:
http://localhost:5000/ham%20egg/page/1
↓(redirection)
http://localhost:5000/ham<b>%2520</b>egg