Add syslog support to the C++ services

This patch allows the C++ opencontrail services to use syslog
like the Python services (as introduced by commit
f316c1c1dd38b3b0cba3a55d47f3cc08edb6aaad), either by
using the --DEFAULT.use_syslog and --DEFAULT.syslog_facility
arguments on the command line, either using the 'use_syslog'
and 'syslog_facility' attributes of the DEFAULTS section of the
configuration file.

Conflicts:
        src/vnsw/agent/cmn/agent_param.cc
        src/vnsw/agent/contrail/main.cc

Change-Id: Iecec889ccd8f334f90104300ed8ad1df2c208b79
Closes-Bug: 1299277
(cherry picked from commit 848173fda5a638bc20660656cdd392bf638acce8)
Merge "Add syslog support to the C++ services" into R1.10