VPN-to-Router Associate/Disas Performance Improve

VPN-to-Router Associate/Disas Performance Improve

Problem Description:
====================
When BGP-VPN is getting associated with router, FIB entries
are getting programmed very slow. This will cause the
performance of the VPN Manager.

Solution:
=========
Delay root cause: Each VPN interface update is taking 2 sec time to
remove the old VPN ID and update the new VPN ID and VPN service
unbind and bound to new VPN Instance.

To avoid each VPN interface update 2sec time delay, have moved
the method "handleVpnSwapForVpnInterface" processing logic into
JobCoordinator to process each VPN interface update in parallel.
This way overall FIB entry update is consuming less time compare
to without having this code change.

Issue: NETVIRT-1182

Change-Id: Ic17cba3e325a0c63fead9d30ec857c0e7eb8dcfc
Signed-off-by: Karthikeyan Krishnan <karthikeyangceb007@gmail.com>