Add service definition to hierarchy.

def add(self):
        """Add service definition to hierarchy."""

        yield self.client.create(self.path)
        yield self.client.create(self.path + "/type", self.name)
        yield self.client.create(self.path + "/state")
        yield self.client.create(self.path + "/machines", "[]")

        log.debug("registered service '%s' at %s." % (self.name, self.path))