config-resilience: re-seed ifmap from api-server on ifmap restart

[Hampapur Ajay]

Currently if ifmap-server restarts, we rely on rules + supervisor to restart api-server too so that ifmap can be re-seeded with information from cassandra db. It is desirable to do this re-seeding without a restart needed of api-server. In effect a health-checker is needed.

[OpenContrail Admin (ci-admin-f)]

Review in progress for https://review.opencontrail.org/14191
Submitter: Hampapur Ajay (<email address hidden>)

[OpenContrail Admin (ci-admin-f)]

Reviewed: https://review.opencontrail.org/14191
Committed: http://github.org/Juniper/contrail-controller/commit/04c8439af0bb3362c8c8fa1d60b3d783430b1980
Submitter: Zuul
Branch: master

commit 04c8439af0bb3362c8c8fa1d60b3d783430b1980
Author: Hampapur Ajay <email address hidden>
Date: Fri Oct 2 09:06:04 2015 -0700

Add health-check from api-server to ifmap and reseed on reconnect.

Add a health-checker greenlet with configurable interval and rely
on existing mechanism to re-seed ifmap on successful DOWN to UP
transition. The greenlet adds a 'healthcheck' identifier to ifmap
(which is not connected to graph - so subscriptions are not impacted).

Change-Id: I73660477f0db28e6e49a927ad52f5fbae868dd4d
Closes-Bug: #1502221