wrap CAcloseSslConnectionFreeEndpoint method with __TIZEN__ flag

wrap CAcloseSslConnectionFreeEndpoint method with __TIZEN__ flag

[Model] IoTivity
[BinType] AP
[Customer] iot-core

[Issue#] CONPRO-1392
[Request] r.chudek
[Occurrence Version] n/a

[Problem] pthread might be not available on other platforms
[Cause & Measure] n/a
[Checking Method] n/a

[Team] IoTConnection
[Developer] g.zakiewicz
[Solution company] Samsung
[Change Type] fix

https://github.sec.samsung.net/RS7-IOTIVITY/IoTivity/pull/414
(cherry picked from 9dc9af2eabffb1d46c1671baa4b0decfeb173a1e)

Change-Id: Idac05cde4018b6b064721c2ada5706601c2cb0c3
Signed-off-by: Abhishek Sansanwal <abhishek.s94@samsung.com>