If docker wait fails, get the exit code using docker inspect

.github/workflows/deploy-gcp-tests.yml

@@ -666,16 +666,20 @@ jobs:
       # `docker wait` can also wait for multiple containers, but we only ever wait for a single container.
       - name: Result of ${{ inputs.test_id }} test
         run: |
-          EXIT_CODE=$(\
           gcloud compute ssh \
           ${{ inputs.test_id }}-${{ env.GITHUB_REF_SLUG_URL }}-${{ env.GITHUB_SHA_SHORT }} \
           --zone ${{ env.ZONE }} \
           --quiet \
           --ssh-flag="-o ServerAliveInterval=5" \
-          --command="docker wait ${{ inputs.test_id }}" \
-          )
-          echo "$EXIT_CODE"
-          exit "$EXIT_CODE"
+          --command=' \
+          EXIT_STATUS=$( \
+          docker wait ${{ inputs.test_id }} || \
+          docker inspect --format "{{.State.ExitCode}}" ${{ inputs.test_id }} || \
+          echo "missing container, or missing exit status for container"
+          ); \
+          echo "docker exit status: $EXIT_STATUS"; \
+          exit "$EXIT_STATUS" \
+          '
 
 
   # create a state image from the instance's state disk, if requested by the caller