Use docker-compose exec -T with ansible tasks

Docker-compose exec allocates a tty by default unlike docker exec. New
Ansible doesn't provision a tty which causes docker-compose exec to fail
under Ansible now. Address this by passing -T to docker-compose exec
commands which stops allocating a tty. We didn't need one to gracefully
stop zuul services.

Change-Id: Ib52f184f771ae4530f6b6531257dda5d8443043c

playbooks/roles/zuul-executor/tasks/graceful.yaml

@@ -9,7 +9,7 @@
   register: executor_container_list
 - name: Gracefully stop Zuul Executor
   shell:
-    cmd: docker-compose exec executor zuul-executor graceful
+    cmd: docker-compose exec -T executor zuul-executor graceful
     chdir: /etc/zuul-executor
   become: true
   become_user: root

playbooks/roles/zuul-merger/tasks/graceful.yaml

@@ -9,7 +9,7 @@
   register: merger_container_list
 - name: Gracefully stop Zuul Merger
   shell:
-    cmd: docker-compose exec merger zuul-merger stop
+    cmd: docker-compose exec -T merger zuul-merger stop
     chdir: /etc/zuul-merger
   become: true
   become_user: root