[webapi][XWALK-1330] Add 78 TCs for audiosystem

- 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
Why not assert_not_equals, or assert_own_property? See https://github.com/w3c/testharness.js/blob/master/docs/api.md#assert_own_propertyobject-property_name-description