Set audio mode back to normal before we abandon the audio focus after

call.

Currently, we set the audio mode back to normal after we abandon the
audio focus when the call disconnected. This may cause audio playback
switching delay after the call.

Bug: b/281841785
Test: Manually test audio switching after call using Youtube music.
Change-Id: I5b2db68b4b4d2420be34295064413d8b70daac7e