Protect against INCALL->RINGING transition in AudioManager

If such a transition occurs, reset to NORMAL first, to prevent the loss
of uplink audio.

Tested with:
1) Answering Call WAITING (before fix in
https://googleplex-android-review.git.corp.google.com/#/c/571861/1 is applied)
2) Receiving an incoming call while in-call tone is still playing

Bug: 18058600
Bug: 18020190
Change-Id: Ib5ec8d202ed6c5d8262853696e8fadfa7a222ac8