timeout does not apply to name resolution

`timeout` does not seem to be respected at all stages in the request. This goes above and beyond incremental data being received issues.

## Expected Result

Call returns after 0.1 s with an error.

## Actual Result

Call hangs for a long time and eventually returns with:
```
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/urllib3/connection.py", line 141, in _new_conn
    (self.host, self.port), self.timeout, **extra_kw)
  File "/usr/local/lib/python3.6/site-packages/urllib3/util/connection.py", line 60, in create_connection
    for res in socket.getaddrinfo(host, port, family, socket.SOCK_STREAM):
  File "/usr/local/lib/python3.6/socket.py", line 745, in getaddrinfo
    for res in _socket.getaddrinfo(host, port, family, type, proto, flags):
socket.gaierror: [Errno -3] Temporary failure in name resolution

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/urllib3/connectionpool.py", line 601, in urlopen
    chunked=chunked)
  File "/usr/local/lib/python3.6/site-packages/urllib3/connectionpool.py", line 357, in _make_request
    conn.request(method, url, **httplib_request_kw)
  File "/usr/local/lib/python3.6/http/client.py", line 1239, in request
    self._send_request(method, url, body, headers, encode_chunked)
  File "/usr/local/lib/python3.6/http/client.py", line 1285, in _send_request
    self.endheaders(body, encode_chunked=encode_chunked)
  File "/usr/local/lib/python3.6/http/client.py", line 1234, in endheaders
    self._send_output(message_body, encode_chunked=encode_chunked)
  File "/usr/local/lib/python3.6/http/client.py", line 1026, in _send_output
    self.send(msg)
  File "/usr/local/lib/python3.6/http/client.py", line 964, in send
    self.connect()
  File "/usr/local/lib/python3.6/site-packages/urllib3/connection.py", line 166, in connect
    conn = self._new_conn()
  File "/usr/local/lib/python3.6/site-packages/urllib3/connection.py", line 150, in _new_conn
    self, "Failed to establish a new connection: %s" % e)
urllib3.exceptions.NewConnectionError: <urllib3.connection.HTTPConnection object at 0x7fcbf63ce0f0>: Failed to establish a new connection: [Errno -3] Temporary failure in name resolution

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/requests/adapters.py", line 440, in send
    timeout=timeout
  File "/usr/local/lib/python3.6/site-packages/urllib3/connectionpool.py", line 639, in urlopen
    _stacktrace=sys.exc_info()[2])
  File "/usr/local/lib/python3.6/site-packages/urllib3/util/retry.py", line 388, in increment
    raise MaxRetryError(_pool, url, error or ResponseError(cause))
urllib3.exceptions.MaxRetryError: HTTPConnectionPool(host='google.com', port=80): Max retries exceeded with url: / (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7fcbf63ce0f0>: Failed to establish a new connection: [Errno -3] Temporary failure in name resolution',))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.6/site-packages/requests/api.py", line 72, in get
    return request('get', url, params=params, **kwargs)
  File "/usr/local/lib/python3.6/site-packages/requests/api.py", line 58, in request
    return session.request(method=method, url=url, **kwargs)
  File "/usr/local/lib/python3.6/site-packages/requests/sessions.py", line 508, in request
    resp = self.send(prep, **send_kwargs)
  File "/usr/local/lib/python3.6/site-packages/requests/sessions.py", line 618, in send
    r = adapter.send(request, **kwargs)
  File "/usr/local/lib/python3.6/site-packages/requests/adapters.py", line 508, in send
    raise ConnectionError(e, request=request)
requests.exceptions.ConnectionError: HTTPConnectionPool(host='google.com', port=80): Max retries exceeded with url: / (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7fcbf63ce0f0>: Failed to establish a new connection: [Errno -3] Temporary failure in name resolution',))
```

## Reproduction Steps

In inside a Docker container with no internet:
```
docker network create --internal --subnet 10.1.1.0/24 no-internet
docker run -it --rm --net no-internet python-with-req
```

```python
import requests
requests.get('http://google.com', timeout=0.1)
```

## System Information

    $ python -m requests.help

```
{
  "chardet": {
    "version": "3.0.4"
  },
  "cryptography": {
    "version": ""
  },
  "idna": {
    "version": "2.6"
  },
  "implementation": {
    "name": "CPython",
    "version": "3.6.4"
  },
  "platform": {
    "release": "4.9.75-linuxkit-aufs",
    "system": "Linux"
  },
  "pyOpenSSL": {
    "openssl_version": "",
    "version": null
  },
  "requests": {
    "version": "2.18.4"
  },
  "system_ssl": {
    "version": "1000114f"
  },
  "urllib3": {
    "version": "1.22"
  },
  "using_pyopenssl": false
}
```

Looks like some others having related issues: https://github.com/requests/requests/issues/290#issuecomment-4795401

Might be an upstream issue in urllib3: https://github.com/shazow/urllib3/issues/1334

This does belong in urllib3