Add designate dashboard to horizon ubuntu/binary

Designate dashboard is not installed in horizon debian/ubuntu
binary image.  But both debian and ubuntu cloudarchive repos
provide python-designate-dashboard package.

Change-Id: I8f65726d14d180368a8f0d349263bd0dd6ef3b90
Closes-Bug: #1702388

docker/horizon/Dockerfile.j2

@@ -52,6 +52,7 @@ RUN sed -i -r 's,^(Listen 80),#\1,' /etc/httpd/conf/httpd.conf \
                 'libapache2-mod-wsgi',
                 'locales',
                 'openstack-dashboard',
+                'python-designate-dashboard',
                 'python-manila-ui',
                 'python-murano-dashboard',
                 'python-sahara-dashboard',