zuul-quick-start: run docker-compose as regular user

To use the buildset registry we need the docker-compose command to
be executed as the zuul user, otherwise the auth configuration is
not set and the test pulls the images from docker.io.
This change also adds the --digests argument to docker image ls.

Change-Id: I62970cae4851b06ff79cdc953f90772c550000bd

playbooks/quick-start/main.yaml

@@ -3,14 +3,13 @@
   shell:
     cmd: docker-compose up -d
     chdir: src/opendev.org/zuul/zuul/doc/source/admin/examples
-  become: true
 - name: Run docker-compose up
   when: local
   shell:
     cmd: docker-compose up -d
     chdir: ../../doc/source/admin/examples
 - name: Print list of images
-  command: docker image ls
+  command: docker image ls --all --digests --no-trunc
 - name: Wait for Gerrit to start
   wait_for:
     host: localhost