Fix pointer checking condition and owner of config file

Fix pointer checking condition and owner of config file

- Issue:
tts_setting_set_voice() does not set voice properly.

- Solution:
Previous code validates the voice with invalid condition. So, the
function returns error even if the voice is valid. Meanwhile, the app
can not write the config file because of the owner of the file. To
resolve these issues, this patch fixes the checking condition and owner
of config file. Through this patch, the function will properly set the
voice.

 To resolve this
issue, this patch fixes the condition as a right way.

Change-Id: I01ac1fd09edb9a10ea365c2376ccf3d6d7a9c4f1
Signed-off-by: Suyeon Hwang <stom.hwang@samsung.com>