Get UID from list using tts_config_client_s structure

Get UID from list using tts_config_client_s structure

Current code converts the type of element as integer. However, the element of the list is instance
of tts_config_client_s structure. Because the first member of the structure is uid, so current code
has no problem until now. But this can occur problem if the type of uid or the order of member is
changed.

To solve this problem, this patch changes the type from integer to the structure. This can provide
safe access to member.

Change-Id: I168011529efec4a59a1a1abc8b7d203e412a4972
Signed-off-by: Suyeon Hwang <stom.hwang@samsung.com>