audio policy: Avoid unintended update of a command's timestamp

- When two setParameter calls with different keyValuePairs reach
  AudioPolicyService from HAL, the timestamp of the command received
  later is updated to that of the command received first.
  This is unintended and might cause a delay or advance the processing
  of commands.
- AudioPolicyService processes setParameters calls in the order
  in which it receives them and when two setParameter calls with
  different keyValuePairs come in (in this case, FM volume with a
  delay and routing), the timestamp of the command received last
  (routing) is updated to be processed at the timestamp of the command
  received earlier (FM volume). FM volume is set with a delay which
  causes the delay in routing as well.
- The timestamp of the command should be updated only if the
  keyValuePairs in the setParameters call match.

CRs-Fixed: 538263

Change-Id: Ie9e7d3ddf9aabd5cf551dccc27aca0a88d1edb77