DNS: generate named config outside contrail-dns

[Hari Prasad Killi]

Currently, contrail-dns generates the configuration file for contrail-named. This necessitates a change in contrail-dns and consequently a new package is required for any change required in the named config.

This can be avoided by taking out the named configuration generation to a script. Contrail-dns provides input to this script either in XML or any other text format and kicks the script to regenerate named configuration.

[Nipa (nipak)]

"contrail-rndc -c /etc/contrail/dns/contrail-rndc.conf reconfig"
can be used to update the contrail-named.conf and apply configs, but these configs
are not saved as we apply add new vdns etc., hence the script so both new configs(i,e views and zones) can be applied and older configurations for under options{} , key {}, logging {}, controls()
stanzas can be replayed on top.

[Nipa (nipak)]

commit 3e720946a2069a3e24c5d5db35f907579bc002a8
Author: Nipa Kumar <email address hidden>
Date: Thu Aug 25 18:38:03 2016 -0700

    Collector stops sending Discovery Publish Message to Discovery Server.

    Discovery Client is waiting infinetly for the "http client" task to be scheduled which
    periodically sends publish message to Discovery Server.

    Both VncApi object and Discovery Client object uses the same "http client" task and instance.
    Deletion of either of the object does not cleanup with WorkQueue and hence the "http client"
    task scheduled to execute the work on the deleted object does not succeed and waits
    forever. Task Scheduler has a task running with the same task-id and instance and hence
    similar tasks are not scheduled.

    Shutdown the work_qeueue on HttpClient object delete.

    Change-Id: Idb44f8106e250c12da3ee9ed30eb1f0ed576d944
    Closes-Bug:1617112