Only run flakey tests on release

Only run flakey tests on release

Fix https://gitlab.com/gitlab-org/gitter/webapp/issues/2062

We don't want to get rid of these tests because they test our integration with GitHub/GitLab end to end. But because these rely on an external API outside of our control, they sometimes fail.

---

gulpfile-test.js

testModules.asdf = {
  files: [path.join('modules', 'github', 'test', 'github-issue-service-test.js')],
  isCritical: true
};

---

Continuation of

• https://gitlab.com/gitlab-org/gitter/webapp/merge_requests/1334
• https://gitlab.com/gitlab-org/gitter/webapp/merge_requests/1337