audio policy: fix disordered sequence while changing device

  Disordered sequence will occur when delayMs of muting volume
  and changing path are the same and no additional delay between
  both commands (muteWaitMs == 0).
  Add half reported latency to delayMs for routing could avoid
  processing muting stream volume and switching path concurrently.

Bug: 149798335
Test: Make VoIP/voice call and switch device between handset/handsfree.
      Check if touch tone is truncated in QXDM.

Signed-off-by: Jasmine Cha <chajasmine@google.com>
Change-Id: Ifa15ba9de330805637cfb20ee96c4293c1c1bd31