Improve data access method of ryu-agent

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