Commit#1
Bug#2989 - agent cored at std::string::assign(std::string const&)

Fix:
For every XMPP channel in agent create a unicast sequence number.
This number will be carried with DB request. In case BGP peer has
changed in channel then the number is incremented and any request not belonging
to
the new sequence number will be ignored.
The information is being sent using data part of request.

Commit#2
Bug 3068 - Security group id zero, even the agent ifmap shows a value '7'.
Skip config with sg id as 0.

Commit#3
Add headless mode config in contrail-vrouter-agent.conf.
Also make the param name consistent to
headless_mode in argument and config.

Change-Id: I55af7d6b1160406c8022bdade0091e9cf12d7563
Merge "Commit#1 Bug#2989 - agent cored at std::string::assign(std::string const&)"