Add env variable to disable qa dev-shm

What does this MR do and why?

Enables local runs to disable the chrome dev-shm-usage. On my linux ubuntu machine (and my previous work one), I've always had to use export CI=true to get the tests to run for longer than a ~15 minutes before running into dev-shm issues.

Related MR in gitlab-qa: gitlab-qa!794 (merged)

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