MAASDispatcher cannot control HTTP method properly

[Gavin Panella]

It uses urllib2, which is fairly difficult to get using the correct HTTP method. Using httplib2 is an easy solution here.

There's a reference to this problem in src/maascli/api.py:

        # Use httplib2 instead of urllib2 (or MAASDispatcher, which is based
        # on urllib2) so that we get full control over HTTP method. TODO:
        # create custom MAASDispatcher to use httplib2 so that MAASClient can
        # be used.
        http = httplib2.Http()
        response, content = http.request(
            uri, self.method, body=body, headers=headers)