Change event class from THREAD_MAIN to THREAD_SUB for capture callback

Change event class from THREAD_MAIN to THREAD_SUB for capture callback

THREAD_MAIN event class is workaround code for TBT test.
It's rollbacked because this commit will make capture callback as syncronously,
then TBT capture issue could not be occurred.
(capture completed callback can be called although capture callback is not returned.)

[Version] 0.2.52
[Profile] Common
[Issue Type] Update
[Dependency module] N/A
[Dependency commit] N/A
[Test] [M(T) - Boot=(OK), sdb=(OK), Home=(OK), Touch=(OK), Version=tizen-mobile_20161007.1]

Change-Id: I6430ccca7c8acf7a2f9b7333f9dc440a8de844ea
Signed-off-by: Jeongmo Yang <jm80.yang@samsung.com>