AudioFlinger: fix FLAG_BYPASS_MUTE

If a track's audio_attributes_t's flags contain
FLAB_BYPASS_MUTE, use the port volume instead of
muting it.

Bug: 415311394
Flag: com.android.media.audio.ring_my_car
Test: atest android.media.audio.cts.AudioPlaybackConfigurationTest#testAudioTrackBypassMute

Change-Id: Ia17784b336797909854ff4cc5dc7c24c01d3a1b6