stream-manager: Improve audio ducking function

stream-manager: Improve audio ducking function

1. Fix crash
: If ducked stream is removed without deactivating,
  the pointer for the removed stream is still remained in idxset of ducking_streams.
  It caused crash when ducking stream is destroyed.

2. Apply ducking to new stream
: If new role-matched stream is created when after ducked,
  apply ducking to it without fade-out.

[Version] 11.1.60
[Issue Type] Improvement

Change-Id: Ida0556e5d8c1d10f001357291ca17193174c26ae
Signed-off-by: Jeongmo Yang <jm80.yang@samsung.com>