Fix forcing webrtcvad by auto-gain/noise-suppression

[chatziko]

--auto--gain and --noise-suppression cause webrtcvad to be used, even under --vad=disabled. It's hard to spot cause this code thinks we don't use vad while this code thinks we do. The PR fixes this.

PS. Out of curiosity, is there a reason why webrtc-noise-gain always enables vad instead of having it configurable? Doesn't it waste cpu?

[synesthesiam]

Thanks!

I believe webrtc-noise-gain always enables VAD because it uses that as the feedback for automatic gain control.