Comment 27 for bug 1684993

Reviewed: https://review.opencontrail.org/44689
Committed: http://github.com/Juniper/contrail-controller/commit/ac4e3970603f491ef400ab0fd408cef9a080e053
Submitter: Zuul (<email address hidden>)
Branch: R3.2.3.x

commit ac4e3970603f491ef400ab0fd408cef9a080e053
Author: Praveen K V <email address hidden>
Date: Thu Apr 20 19:53:48 2017 +0530

Replace tbb::task::spawn() by tbb::task::enqueue() and also support for task monitoring

Replace tbb::task::spawn() by tbb::task::enqueue(). enqueue() is more
appropriate call since task library just fires the task without calling
spawn_root_and_wait()

Also, introduced a TaskMonitor class which monitors number of tasks
enqueued to scheduler and number of tasks spawned by TBB. If the monitor
finds tasks are enqueued but not scheduled for a configured time, it
will exit the program.

Conflicts:
 src/base/task.cc
 src/base/task.h
 src/vnsw/agent/cmn/agent.cc
 src/vnsw/agent/contrail-vrouter-agent.conf
 src/vnsw/agent/init/agent_param.cc

Change-Id: Ia68d52f4aba0e79a3fe75f8c4fc248d49ab94faf
Closes-Bug: #1684993
(cherry picked from commit a2eb06443bcfaef5279f65a6e402fe9bc9f055b7)