AudioService: fix audio mode not reset to MODE_NORMAL

when a app call setMode to set mode to non MODE_NORMAL modes many times with different audio managers in the same process, in this case the "pid" parameters are the same and the "cb" parameters are not the same, then the parameter "cb" registered and the "mCb" in hdlr are not the same, then NoSuchElementException will happen, and when the app was cleared in recent tasks the audio mode will not be reseted to MODE_NORMAL by expected flow.

Signed-off-by: wumin3 <wumin3@xiaomi.com>
Change-Id: Ifb8c66372a8e994edcea628cad7dc2a7ee4763a6