ryu-agent should use rpc

[Yoshihiro Kaneko]

ryu-agent still accesses a database directly. This approach has
already been obsoleted.
Other agents use rpc instead of accessing a database directly.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/20786

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/20786
Committed: http://github.com/openstack/quantum/commit/40e76356dd50113936826833eddb3ce57fee8214
Submitter: Jenkins
Branch: master

commit 40e76356dd50113936826833eddb3ce57fee8214
Author: Yoshihiro Kaneko <email address hidden>
Date: Wed Jan 30 15:50:41 2013 +0900

    Improve data access method of ryu-agent

    fixes bug #1110174

    This patch implement rpc in ryu-agent, instead of accessing a
    database directly.
    Because it was not necessary to transmit information via database,
    therefore the table is eliminated.

    Also, I remove openflow controller stuff from a configuration file
    of the Ryu plugin because it was not used anymore.

    Change-Id: I5e261297c3f92c6a1ac5df229084176e84694e87