[webapi][XWALK-2101]update attribute name for audiosystem

- Fail Reason: The error callback is invoked.

Impacted TCs num(approved): New 0, Update 3, Delete 0
Unit test Platform: [Tizen-IVI]
Test result summary: Pass 0, Fail 3, Blocked 0
Merge pull request #507 from JianfengXu/xujf/audiosystem/2102

[webapi][XWALK-2101]update attribute name for audiosystem