Use tts_ipc function as same way regardless of ipc methods.

Use tts_ipc function as same way regardless of ipc methods.

tts_ipc layer is interface layer.
Thus, developer should not have no interest below the layer.

However, in current code, tts_ipc function is used as different way by the ipc method.
Calling interface as same way is better to read, and if there is difference, the difference should
be covered on implementation layer.

This patch unify the usages of functions in tts_ipc. To unify the usage, this patch also fix the
implementation of each method dbus and tidl.

Change-Id: I557fed82f11cace93f52eb13a9ba37bb9287a38d
Signed-off-by: Suyeon Hwang <stom.hwang@samsung.com>