Route to the previous active input when System Audio Mode is off.

Previously we switched away from ARC input when ARC is terminated in
https://googleplex-android-review.git.corp.google.com/c/platform/frameworks/base/+/5056172

But since ARC and SAM are independent, we do not terminate ARC with SAM
any more and the TV does not need to terminate ARC either.
In this case Audio device with ARC as a TV input and disable muting(Atom)
will still play sound when system audio mode is off.

Test: manual
Bug: 131906139
Change-Id: Ie15a9825a50cc898bc07d5ce707935425ce5ead3
(cherry picked from commit 4acd92066e3c813b3e15628c2aada196c68a51fd)