vDNS published services to reevaluate service periodically

[Nipa]

Discovery Client library now provides support to check status of the published services periodically. vDNS needs to use this feature to reevaluate and update the status of the pubslished service.

vDNS will check the following conditions
1) Connection to named is up
2) End of Config Marker.

vrouter based on xmpp connection to DNS-server assumes named is up and sends queries with retries. This will ensure queries are sent to named only when named is up and listening on port 53.

[OpenContrail Admin (ci-admin-f)]

Review in progress for https://review.opencontrail.org/14653
Submitter: Nipa Kumar (<email address hidden>)

[OpenContrail Admin (ci-admin-f)]

Reviewed: https://review.opencontrail.org/14653
Committed: http://github.org/Juniper/contrail-controller/commit/58949977943ac65b0bd94121a5ead2d94cf19d82
Submitter: Zuul
Branch: master

commit 58949977943ac65b0bd94121a5ead2d94cf19d82
Author: Nipa Kumar <email address hidden>
Date: Mon Oct 26 15:39:48 2015 -0700

Advertise DNS-Server status as up conditionally to discovery-server.

Conditions are based on config read completely from IfMap Server
and connection to named is UP.

Added checks for pid recirculation by associating to named process.
(diffs from Hari Prasad Killi)

Change-Id: I24510c77ac1fa00dfcc48b4ac087e7cc164bc579
Closes-Bug:1477742
Closes-Bug:1489610