Comment 9 for bug 1533627

Reviewed: https://review.opencontrail.org/16523
Committed: http://github.org/Juniper/contrail-controller/commit/4a4bb3d5b8af10b15a2c4776ea077778c51284bb
Submitter: Zuul
Branch: master

commit 4a4bb3d5b8af10b15a2c4776ea077778c51284bb
Author: Prabhjot Singh Sethi <email address hidden>
Date: Tue Jan 26 23:51:34 2016 +0530

Fix Healtcheck instance parallel access & cleanup

Issue:
------
Health check instance is getting access from asio and
DBtable task context causing race condition to access
object and delete it at the same time.

Fix:
----
- move operation for READ and EXIT to a new HealthCheck
task context which runs in exclusion with DBTable task
- move cleanup of instance from DBTable to HealthCheck
task context to put events in correct sequence
- instance holds reference to service object to assure
sanity of access till cleanup is complete

Closes-Bug: 1533627
Related-Bug: 1530539
Change-Id: I2880a2c21a8a642bd6612067be5b67ba02c88fe8