Audio policy: fix volume change on DEVICE_OUT_SPEAKER_SAFE

When changing stream volume, compare given device and current device
  for stream both as filtered through Volume::getDeviceForVolume.
This behavior matters for Android devices playing notifications and
  ringtones on the AUDIO_DEVICE_OUT_SPEAKER_SAFE, which is filtered
  out for volumes (see Volume.h for getDeviceForVolume() method).

Test: play a ringtone and modify volume with vol keys
Bug: 63004956
Change-Id: I139099f34e0ab091fd0ea761c75949656549f77a