Add mutex for thread safety of app_data access

Add mutex for thread safety of app_data access

app_data can be handled by main thread and sub thread for text playing.
Previous code guarantees the thread safety of sound data and speak data.
However, these are members of app data and thread safety of app data is not guaranteed.

This patch make mutex for app data access and unifies the mutex g_speak_data_mutex and
g_sound_data_mutex. These mutex are covered by new mutex for app data, because the data
covered by previous mutexs are member of app data.
So, if app wants to access those data, it should access app data first.

Change-Id: Ifb42b4e4751c32e3d8f786f79ffc3871b3c273e7
Signed-off-by: Suyeon Hwang <stom.hwang@samsung.com>