[webapi][XWALK-1330] Add 78 tests for Audio System API

- Add 78 TCs for audiosystem
- Audiosystem is not supported in Tizen IVI now.

Impacted TCs (designed): New 78, Update 0, Delete 0
Unit test Platform: Tizen IVI
IVI test result summary: Pass 0, Fail 0, Blocked 0
If you have different functions in common, please create new support file like `webapi/tct-content-tizen-tests/content/support/content_common.js` rather than update `unitcommon.js`!