Fix FindGroup API of Things Manager about group sync feature.
It is not notify about state of finding to caller.
So we will return 'OC_STACK_ERROR' when It was finding a group.
User should be wait findCallback.
Then user will know the result of finding.
FindCallback has the argument which OCResource.
If it is NULL we could not find a group.
Fix [IOT-286]
Change-Id: I2b95d5102e54e4242394c36d51de81f192b87e13
Signed-off-by: HyunJun Kim <hyunjun2.kim@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/230
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Uze Choi <uzchoi@samsung.com>