Digest Authentication wrong password bug

When using digest authentication with a wrong password, requests will retry the request for infinity. 
This code snippet will run forever:

```
import requests
from requests.auth import HTTPDigestAuth
requests.get('http://httpbin.org/digest-auth/auth/user/passwd', auth=HTTPDigestAuth('user', 'incorrect'))
```


Gah, I forgot about this bug. 


Closeable, right?


@slingamn you're a machine


FWIW, I am still seeing this bug on 0.13.0. Stack dump below:

```
>>> import requests
>>> from requests.auth import HTTPDigestAuth
>>> url = 'http://REDACTED'
>>> auth = HTTPDigestAuth('foo', 'bar')
>>> r = requests.get(url, auth=auth)
Traceback (most recent call last):
  File "/Users/coj/Dropbox/Sites/dnd-auth-test/venv/lib/python2.7/site-packages/requests/hooks.py", line 47, in dispatch_hook
    hook_data = hook(hook_data) or hook_data
  File "/Users/coj/Dropbox/Sites/dnd-auth-test/venv/lib/python2.7/site-packages/requests/auth.py", line 219, in handle_401
    r.request.send(anyway=True)
  File "/Users/coj/Dropbox/Sites/dnd-auth-test/venv/lib/python2.7/site-packages/requests/models.py", line 602, in send
    timeout=self.timeout,
  File "/Users/coj/Dropbox/Sites/dnd-auth-test/venv/lib/python2.7/site-packages/requests/packages/urllib3/connectionpool.py", line 384, in urlopen
    body=body, headers=headers)
  File "/Users/coj/Dropbox/Sites/dnd-auth-test/venv/lib/python2.7/site-packages/requests/packages/urllib3/connectionpool.py", line 254, in _make_request
    conn.request(method, url, **httplib_request_kw)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/httplib.py", line 941, in request
    self._send_request(method, url, body, headers)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/httplib.py", line 975, in _send_request
    self.endheaders(body)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/httplib.py", line 937, in endheaders
    self._send_output(message_body)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/httplib.py", line 797, in _send_output
    self.send(msg)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/httplib.py", line 759, in send
    self.connect()
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/httplib.py", line 740, in connect
    self.timeout, self.source_address)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/socket.py", line 557, in create_connection
    sock = socket(af, socktype, proto)
RuntimeError: maximum recursion depth exceeded
```


Just to follow-up, similar results in 0.13.1:

```
>>> import requests
>>> requests.__version__
'0.13.1'
>>> from requests.auth import HTTPDigestAuth
>>> url = 'http://funkatron.com/digest-test/'
>>> auth = HTTPDigestAuth('foo', 'bar')
>>> r = requests.get(url, auth=auth)
Traceback (most recent call last):
  File "/Users/coj/Documents/gbvm-3.0/donenotdone.com/frontend/venv/lib/python2.7/site-packages/requests/hooks.py", line 46, in dispatch_hook
    _hook_data = hook(hook_data)
  File "/Users/coj/Documents/gbvm-3.0/donenotdone.com/frontend/venv/lib/python2.7/site-packages/requests/auth.py", line 219, in handle_401
    r.request.send(anyway=True)
  File "/Users/coj/Documents/gbvm-3.0/donenotdone.com/frontend/venv/lib/python2.7/site-packages/requests/models.py", line 609, in send
    raise ConnectionError(e)
ConnectionError: HTTPConnectionPool(host='funkatron.com', port=80): Max retries exceeded with url: /digest-test/
```


Is there any workaround for this issue?