push-to-trigger-integration script breaks post-artifact step

[acmiyaguchi]

Running the push-to-trigger-integration script will cause CircleCI to fail. This is due to a new dependency on a BigQuery diff that was introduced in #525.

The CI in #533 fails with the following error:

#!/bin/bash -eo pipefail
.circleci/post-artifact.js

[ '6958836.report.json',
  'a048403-6958836.diff',
  'a048403.report.json' ]
fs.js:904
  return binding.readdir(pathModule._makeLong(path), options.encoding);
                 ^

Error: ENOENT: no such file or directory, scandir '/tmp/integration'
    at Object.fs.readdirSync (fs.js:904:18)
    at bigquery_diff (/home/circleci/project/.circleci/post-artifact.js:50:20)
    at Object.<anonymous> (/home/circleci/project/.circleci/post-artifact.js:76:3)
    at Module._compile (module.js:652:30)
    at Object.Module._extensions..js (module.js:663:10)
    at Module.load (module.js:565:32)
    at tryModuleLoad (module.js:505:12)
    at Function.Module._load (module.js:497:3)
    at Function.Module.runMain (module.js:693:10)
    at startup (bootstrap_node.js:188:16)

https://circleci.com/gh/mozilla-services/mozilla-pipeline-schemas/3380

This is caused by the lack of the workspace upload in the test step.

mozilla-pipeline-schemas/.circleci/config.yml

Lines 119 to 123 in a048403

	- test:
	filters:
	branches:
	# This branch is only used for the .github/push-to-trigger-integration script
	ignore: trigger-integration