Comment 80 for bug 1684993

Reviewed: https://review.opencontrail.org/46325
Committed: http://github.com/Juniper/contrail-third-party/commit/5cf3f4c78dcb2718218be2d27d9d247290f6c8c5
Submitter: Vinay Vithal Mahuli (<email address hidden>)
Branch: R3.2.3.x

commit 5cf3f4c78dcb2718218be2d27d9d247290f6c8c5
Author: Ananth Suryanarayana <email address hidden>
Date: Wed Sep 19 14:19:17 2018 -0700

Do not insert already sleeping tbb task back into sleeping list

During testing, it was found that tbb sleeping threads singly linked
list was corrupted and had become circular. This seemingly caused
my_slack count to get permanently stuck at -1, as the sleeping list
traversal would potentially never end.

During testing, using a specific assert, it was confirmed that duplicate
insertion did happen.

Fixed it by modifying the sleeing threads singly linked list into a
doubly linked list and then making sure that a thread if already in
the list is never prepended back as the head of the list.

https://github.com/01org/tbb/issues/86

Closes-Bug: #1684993
Change-Id: I6773eb8dddd849cebb695a59864a9da2ce2faa17
Depends-On: Iec821e3b08c3825cf2789a70bf53621650c66516