audio: Fix glitching of remote submix

Align behavior with the HIDL implementation. This helps
to prevent glitches in the scenarios that use remote
submix for sending audio externally: Auto and Cast.

Bug: 322247032
Bug: 327220024
Test: Repro steps in b/327220024#comment14
Change-Id: If2e4ebd7145375a268ee5f0e4ab656bb3748b2fe