Robustified the detection of linear filter quality in AEC3

BUG=webrtc:8141

Review-Url: https://codereview.webrtc.org/3000383002
Cr-Original-Commit-Position: refs/heads/master@{#19468}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 0fcb74d7490f975c717c85ade354ccfe50d1b77a
1 file changed