Fix enrollee sample application's crach issue

Fix enrollee sample application's crach issue

Before OCStop() is called, listen thread for calling OCProcess() should
be terminated.

Change-Id: Ibe4f702bb7c71beaf8bb58a8fe21acb873ad06d6
Signed-off-by: Jihun Ha <jihun.ha@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/13583
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Heewon Park <h_w.park@samsung.com>
Reviewed-by: Madan Lanka <lanka.madan@samsung.com>
(cherry picked from commit 9331e5eddab194f9f17bf09c3b0c70da5c87ab77)
Reviewed-on: https://gerrit.iotivity.org/gerrit/13593
Reviewed-by: Uze Choi <uzchoi@samsung.com>