Add Docker Hub credentials to system tests task

Closes gh-35213

Author: wilkinsona

ci/tasks/run-system-tests.yml

@@ -20,6 +20,10 @@ run:
   args:
     - -ec
     - |
+      mkdir -p /root/.docker
+      cat > /root/.docker/config.json <<EOF
+      { "auths": { "https://index.docker.io/v1/": { "auth": "$DOCKER_HUB_AUTH" }}}
+      EOF
       source /docker-lib.sh
       start_docker $DOCKER_HUB_MIRROR
       ${PWD}/git-repo/ci/scripts/run-system-tests.sh