Set default value to mAttributes in AudioTrack

mAttributes in AudioTrack can not be set in AudioTrack::set()
when pAttributes is NULL.
AudioTrack::getPosition() sometimes returns wrong value
since mAttributes is undefined value.
This change sets default values to mAttributes.

Bug: 123607740
Test: manual
Change-Id: Ie590c17efc466cc89cbd7e9f89fc3ebeed98eace
1 file changed