Test run hangs with IE 11 + Browserstack

[jason0x43]

Expected behavior

The tests should run to completion on Browserstack.

Current behavior

When the tests are run on Browserstack, the IE 11 session sometimes hangs indefinitely. It can be unstuck by making the session interactive in the Browserstack console.

Steps to reproduce (for bugs)

1. Clone this repo
2. Checkout the completed branch
3. npm install, then npm install intern@4.4.1
4. npm test

Environment

Example (e.g., dojo, backbone, etc.):
Intern version: 4.4.1
Node version: 11.10.0
NPM version: 6.8.0
Browser version: IE 11 on Browserstack