IOError from unit tests in disable_internet.py in localhost check

On a Linux Server at work when I run the Astropy unit tests I get
```
args = (('www-cache.mpi-hd.mpg.de', 3128), 3.0, None), kwargs = {}, host = 'www-cache.mpi-hd.mpg.de', valid_hosts = ('localhost', '127.0.0.1'), h = '127.0.0.1'
 
    def new_function(*args, **kwargs):
        if isinstance(args[0], socket.socket):
            host = args[1][0]
            valid_hosts = ('localhost', '127.0.0.1', '::1')
        else:
            host = args[0][0]
            valid_hosts = ('localhost', '127.0.0.1')
        if any([h in host for h in valid_hosts]):
            return original_function(*args, **kwargs)
        else:
>           raise IOError("An attempt was made to connect to the internet "
                          "by a test that was not marked `remote_data`.")
E           IOError: An attempt was made to connect to the internet by a test that was not marked `remote_data`.
 
astropy/tests/disable_internet.py:28: IOError
```


This occurs in two places:
* `test_localconnect_succeeds` in `astropy/tests/tests/test_socketblocker.py:51`
* `TestWebProfile.test_web_profile` in `astropy/vo/samp/tests/test_web_profile.py:77`

Full output here: https://gist.github.com/cdeil/10577755

For some reason the institute HTTP proxy (`www-cache.mpi-hd.mpg.de`) is passed as `host` on this machine instead of `localhost` or `127.0.0.1`.

@astrofrog @keflavich What's the right fix here? Should I mark the tests as `remote_data` or do I need to set some HTTP configuration or do you want to rewrite the check in `disable_internet.py` somehow?