Allow to register multiple callbacks in MediaSessionManager

Bug: 126758528
Test: manually
Change-Id: I613593a88c115a5ac694b8c984f3ae36e9cc1c78
Merged-In: I613593a88c115a5ac694b8c984f3ae36e9cc1c78
(cherry picked from commit 14ddf75c473a6cea391bd74d1638d9d28bcc9b01)
4 files changed