Example docker-compose: support podman

Podman can be used to deploy the example compose instead of Docker.
Podman enforces short name resolution by default, so specify domain
name for the images pulled by the compose.

Change-Id: Ida4033bb48ec98b08a9ce1c54e2675beeff1e44b

doc/source/examples/docker-compose.yaml

@@ -4,14 +4,14 @@ version: '2'
 
 services:
   gerrit:
-    image: gerritcodereview/gerrit
+    image: docker.io/gerritcodereview/gerrit
     ports:
       - "8080:8080"
       - "29418:29418"
     environment:
       - CANONICAL_WEB_URL=http://localhost:8080/
   gerritconfig:
-    image: zuul/zuul-executor
+    image: docker.io/zuul/zuul-executor
     environment:
       - http_proxy
       - https_proxy
@@ -28,7 +28,7 @@ services:
     # default version of ansible for Zuul.
     command: "/usr/local/lib/zuul/ansible/2.9/bin/ansible-playbook /var/playbooks/setup.yaml"
   zk:
-    image: zookeeper
+    image: docker.io/zookeeper
     hostname: examples_zk_1.examples_default
     volumes:
       - "./playbooks/:/var/playbooks/:z"
@@ -36,7 +36,7 @@ services:
       - "./zoo.cfg:/conf/zoo.cfg:z"
     command: "sh -c '/var/playbooks/wait-to-start-certs.sh && zkServer.sh start-foreground'"
   mysql:
-    image: mariadb
+    image: docker.io/mariadb
     environment:
       MYSQL_ROOT_PASSWORD: rootpassword
       MYSQL_DATABASE: zuul
@@ -60,7 +60,7 @@ services:
              zuul-scheduler -f'
     # FIXME: The scheduler has no ansible anymore so use the executor image.
     #        This needs to be changes such that ansible is not required for startup.
-    image: zuul/zuul-scheduler
+    image: docker.io/zuul/zuul-scheduler
     volumes:
       - "./etc_zuul/:/etc/zuul/:z"
       - "./playbooks/:/var/playbooks/:z"
@@ -76,7 +76,7 @@ services:
       - mysql
     ports:
       - "9000:9000"
-    image: zuul/zuul-web
+    image: docker.io/zuul/zuul-web
     environment:
       ZUUL_MYSQL_PASSWORD: secret
     volumes:
@@ -92,7 +92,7 @@ services:
       - ZUUL_MYSQL_PASSWORD=secret
     depends_on:
       - scheduler
-    image: zuul/zuul-executor
+    image: docker.io/zuul/zuul-executor
     volumes:
       - "./etc_zuul/:/etc/zuul/:z"
       - "./playbooks/:/var/playbooks/:z"
@@ -113,7 +113,7 @@ services:
   launcher:
     depends_on:
       - zk
-    image: zuul/nodepool-launcher
+    image: docker.io/zuul/nodepool-launcher
     volumes:
       - "./playbooks/:/var/playbooks/:z"
       - "./etc_nodepool/:/etc/nodepool/:z"

doc/source/examples/logs-Dockerfile

@@ -1,3 +1,3 @@
-FROM httpd:alpine
+FROM docker.io/httpd:alpine
 
 COPY ./httpd.conf /usr/local/apache2/conf/httpd.conf

doc/source/examples/node-Dockerfile

@@ -1,4 +1,4 @@
-FROM ubuntu:20.04
+FROM docker.io/ubuntu:20.04
 
 RUN apt-get update \
     && DEBIAN_FRONTEND="noninteractive" apt-get -y install \