Migrate log_{file,dir} params to neutron class

The log_{dir,file} params was configured in the neutron class::server,
these parameters was not available classes neutron::agent::*
This patch fixes this.

(cherry picked from commit c751443f4fef5e71c0246b5410a2b712aeb656d4)
Closes-bug: #1282296
Change-Id: I205b0ed5db08199000ec11b2212afedf67bf2ed7