[Tizen] Fix wrongly passed variable to function in audiosystem

js_reply variable was prepared, but instead of it js_message was
passed to PostMessage function. Some other nits were fixed.

Change-Id: Id19978ecd38c516c8e16aea3749796fd9400748f
Merge pull request #427 from piotrowskim/rm_unused_audiosystem

[Tizen] Fix wrongly passed variable to function in audiosystem