Makes Floodlight's Static Flow Pusher compliant with REST Spec

Floodlight's Static Flow Pusher REST interface expects "posted data"
for DELETE requests. It uses this posted data to identify which entry
should be deleted. However, the HTTP spec states that resources
to be deleted using the DELETE method should be identified by a
URI (not by posted data):
http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html#sec9.7

This is a problem when you try to use a spec-compliant framework to
communicate with the REST interface provided by StaticFlowEntryPusher
module. The Restlet framework for example, that is being used in the
implementation of the module itself, is an example. It prevents you
from posting data with a DELETE method, as expected by the HTTP spec.