Correct usage of is_banned_domain in api.py

I'm currently getting a 500 error when I try to submit a link.
The fix was to correct a call to is_banned_domain within api.py so that it matched the change made in  b2d5689267d27adac312f00f06be59dfd8e4648e

```
Error - <type 'exceptions.TypeError'>: is_banned_domain() takes exactly 1 argument (2 given)
URL: https://reddit.trustwave.com/api/submit
File '/usr/lib/python2.7/dist-packages/weberror/errormiddleware.py', line 162 in __call__
  app_iter = self.application(environ, sr_checker)
File '/home/reddit/reddit/r2/r2/config/middleware.py', line 206 in __call__
  return self.app(environ, start_response)
File '/home/reddit/reddit/r2/r2/config/middleware.py', line 265 in __call__
  return self.app(environ, start_response)
File '/home/reddit/reddit/r2/r2/config/middleware.py', line 223 in __call__
  return self.app(environ, start_response)
File '/home/reddit/reddit/r2/r2/config/middleware.py', line 238 in __call__
  return self.app(environ, start_response)
File '/home/reddit/reddit/r2/r2/config/middleware.py', line 343 in __call__
  return self.app(environ, start_response)
File '/home/reddit/reddit/r2/r2/config/middleware.py', line 369 in __call__
  return self.app(environ, custom_start_response)
File '/usr/lib/pymodules/python2.7/routes/middleware.py', line 130 in __call__
  response = self.app(environ, start_response)
File '/usr/lib/pymodules/python2.7/pylons/wsgiapp.py', line 125 in __call__
  response = self.dispatch(controller, environ, start_response)
File '/usr/lib/pymodules/python2.7/pylons/wsgiapp.py', line 324 in dispatch
  return controller(environ, start_response)
File '/home/reddit/reddit/r2/r2/lib/base.py', line 127 in __call__
  return WSGIController.__call__(self, environ, start_response)
File '/usr/lib/pymodules/python2.7/pylons/controllers/core.py', line 221 in __call__
  response = self._dispatch_call()
File '/usr/lib/pymodules/python2.7/pylons/controllers/core.py', line 172 in _dispatch_call
  response = self._inspect_call(func)
File '/usr/lib/pymodules/python2.7/pylons/controllers/core.py', line 107 in _inspect_call
  result = self._perform_call(func, args)
File '/usr/lib/pymodules/python2.7/pylons/controllers/core.py', line 60 in _perform_call
  return func(**args)
File '/home/reddit/reddit/r2/r2/lib/validator/validator.py', line 234 in newfn
  simple_vals, param_vals, *a, **kw)
File '/home/reddit/reddit/r2/r2/lib/validator/validator.py', line 304 in validatedForm
  *a, **kw)
File '/home/reddit/reddit/r2/r2/lib/validator/validator.py', line 283 in _validatedForm
  val = self_method(self, form, responder, *a, **kw)
File '/home/reddit/reddit/r2/r2/controllers/api.py', line 357 in POST_submit
  banmsg = is_banned_domain(url, request.ip)
TypeError: is_banned_domain() takes exactly 1 argument (2 given)
```