Fix [IoT-265] issue for Group.

Fix [IoT-265] issue for Group.

FindGroup can not support callback correctly.
It was check the duplication of resource as wrong method. so if resource was duplicated It did ignore the response.

So we change the checking logic for duplication.
Fix [IoT-265].

Change-Id: I27a58a9be688da172043439f62d1694aaaf10c96
Signed-off-by: HyunJun Kim <hyunjun2.kim@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/872
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Uze Choi <uzchoi@samsung.com>