Allow logging to syslog

This patch allows the opencontrail services to use syslog, either
by using the --use_syslog and --syslog_facility arguments on the
command line, either using the 'use_syslog' and 'syslog_facility'
attributes of the DEFAULTS section of the configuration file

Change-Id: Iba368751c9c4ccbf78146286b9499cbf1fe0af80
Closes-Bug: 1299277
(cherry picked from commit f316c1c1dd38b3b0cba3a55d47f3cc08edb6aaad)