[webapi][XWALK-2101] Add audio playback for audiosytem

- Fail Reason: Its not playing using pulseaudio by launching from xwalk-launcher.

Impacted TCs num(approved): New 0, Update 8, Delete 0
Unit test Platform: [Tizen IVI]
Unit test result summary: Pass 0, Fail 8, Blocked 0
Merge pull request #721 from JianfengXu/xujf/2101

[webapi][XWALK-2101] Add audio playback for audiosytem