no way to disable DNSSEC explicitly

[Nobuto Murata]

In some cases, users might want to disable DNSSEC explicitly especially in restricted network which cannot reach to root DNS servers, or upstream DNS server in an organization does not support DNSSEC.

It would be nice if the charm offers a way to optionally disable DNSSEC.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/587511

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/587511
Committed: https://git.openstack.org/cgit/openstack/charm-designate-bind/commit/?id=8d1285104a284ce0e1a073ae27c9f2d5cbb0603e
Submitter: Zuul
Branch: master

commit 8d1285104a284ce0e1a073ae27c9f2d5cbb0603e
Author: Nobuto Murata <email address hidden>
Date: Wed Aug 1 00:55:32 2018 +0900

    Allow disabling dnssec-validation

    This option may be helpful in a situation that upstream DNS servers do
    not support DNSSEC, and BIND9 reports "Unable to fetch DNSKEY". For
    production deployments, it's encouraged to keep DNSSEC enabled.

    Change-Id: I1c28a65ff7d8063ada795b7b2e962fbfedc32c3d
    Closes-Bug: #1784599