Fix trigger for Ubuntu CI jobs

docker/bind9/ubuntu-template symlinks to docker/bind9/debian-template,
so GitLab CI will never trigger any Ubuntu jobs automatically unless the
symlink itself changes.  Ensure Ubuntu jobs are triggered when
docker/bind9/debian-template is modified, to reflect actual Dockerfile
dependencies.

.gitlab-ci.yml

@@ -310,7 +310,7 @@ ubuntu:xenial:amd64:docker:
       when: always
     - if: '$CI_PIPELINE_SOURCE == "merge_request_event" || $CI_PIPELINE_SOURCE == "push" && $CI_COMMIT_REF_NAME == $CI_DEFAULT_BRANCH'
       changes:
-        - docker/bind9/ubuntu-template/*
+        - docker/bind9/debian-template/*
       when: always
 
 ubuntu:bionic:amd64:docker:
@@ -328,7 +328,7 @@ ubuntu:bionic:amd64:docker:
       when: always
     - if: '$CI_PIPELINE_SOURCE == "merge_request_event" || $CI_PIPELINE_SOURCE == "push" && $CI_COMMIT_REF_NAME == $CI_DEFAULT_BRANCH'
       changes:
-        - docker/bind9/ubuntu-template/*
+        - docker/bind9/debian-template/*
       when: always
 
 debian:sid:i386:docker: