The tests for policy_AudioOutputAllowed.False_Block are failing occasionally due to the difference between muted and unmuted state when the machine has audio output disabled by policy is too wide.

On most machines, the difference between these states is very small, around 0.0003 RMS. On some devices though, I am seeing RMS differences as big as 0.08.

Stainless: https://stainless.corp.google.com/search?view=list&first_date=2018-05-16&last_date=2018-05-22&test=policy_AudioOutputAllowed.False_Block&status=FAIL&status=ERROR&reason=RMS+difference+too+wide&exclude_cts=false&exclude_not_run=false&exclude_non_release=true&exclude_au=true&exclude_acts=true&exclude_retried=true&exclude_non_production=false


## Action Items
1. Test device manually [done]
    No static or other audio detected.
2. File request to have loopback dongles on failing machines changed out in case they are defective. [done b/80150999]
3. Up RMS threshold to 0.1 if above steps fail.