[server/session] remove json dumps around call_service
This backouts changeset b151beea9cb6. With call_service being
in-process and synchronous, there's no RPC use case.
# -*- coding: utf-8 -*-
# copyright %(year)s %(author)s, all rights reserved.
# contact %(author-web-site)s -- mailto:%(author-email)s
#
%(long-license)s
"""%(distname)s specific hooks and operations"""