Signal API makes POST body mandatory

When posting to a signal URL, the body should not be mandatory, and we fail with a big ugly stacktrace if you try to post without a body:

# curl -X POST "http://127.0.0.1:8000/v1/signal/arn%3Aopenstack%3Aheat%3A%3A8451068ec4d84d1a865334243675593b%3Astacks%2Ftest_stack7%2F5e8ea9e0-0c6f-4db8-b0e1-84dc435aa8aa%2Fresources%2Finstance_restarter?Timestamp=2013-09-27T10%3A51%3A06Z&SignatureMethod=HmacSHA256&AWSAccessKeyId=e43e800726fb419cbe74bc8655b99659&SignatureVersion=2&Signature=oEIwrcfBAyTaVFp62VRG0WAVmahd0cHzGVFsVLslHPA%3D"
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/eventlet/wsgi.py", line 384, in handle_one_response
    result = self.application(self.environ, start_response)
  File "/usr/lib/python2.7/site-packages/WebOb-1.2.3-py2.7.egg/webob/dec.py", line 130, in __call__
    resp = self.call_func(req, *args, **self.kwargs)
  File "/usr/lib/python2.7/site-packages/WebOb-1.2.3-py2.7.egg/webob/dec.py", line 195, in call_func
    return self.func(req, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/heat/common/wsgi.py", line 367, in __call__
    response = req.get_response(self.application)
  File "/usr/lib/python2.7/site-packages/WebOb-1.2.3-py2.7.egg/webob/request.py", line 1296, in send
    application, catch_exc_info=False)
  File "/usr/lib/python2.7/site-packages/WebOb-1.2.3-py2.7.egg/webob/request.py", line 1260, in call_application
    app_iter = application(self.environ, start_response)
  File "/usr/lib/python2.7/site-packages/WebOb-1.2.3-py2.7.egg/webob/dec.py", line 144, in __call__
    return resp(environ, start_response)
  File "/usr/lib/python2.7/site-packages/keystoneclient/middleware/auth_token.py", line 545, in __call__
    return self.app(env, start_response)
  File "/usr/lib/python2.7/site-packages/WebOb-1.2.3-py2.7.egg/webob/dec.py", line 130, in __call__
    resp = self.call_func(req, *args, **self.kwargs)
  File "/usr/lib/python2.7/site-packages/WebOb-1.2.3-py2.7.egg/webob/dec.py", line 195, in call_func
    return self.func(req, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/heat/common/wsgi.py", line 367, in __call__
    response = req.get_response(self.application)
  File "/usr/lib/python2.7/site-packages/WebOb-1.2.3-py2.7.egg/webob/request.py", line 1296, in send
    application, catch_exc_info=False)
  File "/usr/lib/python2.7/site-packages/WebOb-1.2.3-py2.7.egg/webob/request.py", line 1260, in call_application
    app_iter = application(self.environ, start_response)
  File "/usr/lib/python2.7/site-packages/WebOb-1.2.3-py2.7.egg/webob/dec.py", line 144, in __call__
    return resp(environ, start_response)
  File "/usr/lib/python2.7/site-packages/Routes-1.12.3-py2.7.egg/routes/middleware.py", line 131, in __call__
    response = self.app(environ, start_response)
  File "/usr/lib/python2.7/site-packages/WebOb-1.2.3-py2.7.egg/webob/dec.py", line 144, in __call__
    return resp(environ, start_response)
  File "/usr/lib/python2.7/site-packages/WebOb-1.2.3-py2.7.egg/webob/dec.py", line 130, in __call__
    resp = self.call_func(req, *args, **self.kwargs)
  File "/usr/lib/python2.7/site-packages/WebOb-1.2.3-py2.7.egg/webob/dec.py", line 195, in call_func
    return self.func(req, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/heat/common/wsgi.py", line 670, in __call__
    raise exception.HTTPExceptionDisguise(http_exc)
HTTPExceptionDisguise

In the api-cfn.log:

resources/instance_restarter'} __call__ /usr/lib/python2.7/site-packages/Routes-1.12.3-py2.7.egg/routes/middleware.py:103
2013-09-27 11:51:28.405 12107 ERROR root [-] Exception handling resource: signal() takes exactly 4 arguments (3 given)

Fix is to default the body to None in the controller