Add POLQA to low bandwidth audio test

BUG=webrtc:7229

Review-Url: https://codereview.webrtc.org/2804083003
Cr-Original-Commit-Position: refs/heads/master@{#17671}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: f2501004759a8d634ae5b2426e76ec0c8e5b557a
3 files changed