message: build(aio): minor `update-preview-server.sh` improvements
diff: set -eux -o pipefail
  exec 3>&1
  +echo "[`date`] - Updating the preview server..."
  +
  # Input
  readonly HOST_REPO_DIR=$1
  readonly HOST_LOCALCERTS_DIR=$2
  @@ -17,8 +19,6 @@ readonly CONTAINER_NAME=aio
  # Run
  (
  - echo "[`date`] - Updating the preview server..."
  -
  cd "$HOST_REPO_DIR"
  readonly lastDeployedCommit=$(git rev-parse HEAD)
  @@ -27,17 +27,18 @@ readonly CONTAINER_NAME=aio
  # Pull latest master from origin.
  git pull origin master
  - # Do not update the server unless files inside `aio-builds-setup/` have changed.
  + # Do not update the server unless files inside `aio-builds-setup/` have changed
  + # or the last attempt failed (identified by the provisional image still being around).
  readonly relevantChangedFilesCount=$(git diff --name-only $lastDeployedCommit...HEAD | grep -P "^aio/aio-builds-setup/" | wc -l)
  - if [[ $relevantChangedFilesCount -eq 0 ]]; then
  + readonly lastAttemptFailed=$(sudo docker rmi "$PROVISIONAL_IMAGE_NAME" >> /dev/fd/3 && echo "true" || echo "false")
  + if [[ $relevantChangedFilesCount -eq 0 ]] && [[ "$lastAttemptFailed" != "true" ]]; then
  echo "Skipping update because no relevant files have been touched."
  exit 0
  fi
  # Create and verify a new docker image.
  - sudo docker rmi "$PROVISIONAL_IMAGE_NAME" || true
  aio/aio-builds-setup/scripts/create-image.sh "$PROVISIONAL_IMAGE_NAME"
  - readonly imageVerified=$(sudo docker run --dns 127.0.0.1 --rm --volume $HOST_SECRETS_DIR:/aio-secrets:ro "$PROVISIONAL_IMAGE_NAME" /bin/bash -c "aio-init && aio-health-check && aio-verify-setup" > /dev/fd/3 && echo "true" || echo "false")
  + readonly imageVerified=$(sudo docker run --dns 127.0.0.1 --rm --volume $HOST_SECRETS_DIR:/aio-secrets:ro "$PROVISIONAL_IMAGE_NAME" /bin/bash -c "aio-init && aio-health-check && aio-verify-setup" >> /dev/fd/3 && echo "true" || echo "false")
  if [[ "$imageVerified" != "true" ]]; then
  echo "Failed to verify new docker image. Aborting update!"
  