Add unittest test-case for cafragmentation code.

Add unittest test-case for cafragmentation code.

Signed-off-by: jaehyun Cho <jaehyun3.cho@samsung.com>
Change-Id: Id98b2151b8149d892d1e063ca893c85fd672af50
Reviewed-on: https://gerrit.iotivity.org/gerrit/14353
Reviewed-by: Jaehong Jo <jaehong.jo@samsung.com>
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: jihwan seo <jihwan.seo@samsung.com>
Reviewed-by: Phil Coval <philippe.coval@osg.samsung.com>
Reviewed-by: Dan Mihai <Daniel.Mihai@microsoft.com>
Reviewed-by: Ashok Babu Channa <ashok.channa@samsung.com>