Check parsing response from cjson

Check parsing response from cjson

Prevent crash if invalid json response received from server.

Change-Id: I339796be64ca4ec46d2e68a02b7f128a8c2fcdab
Signed-off-by: Abhishek Sharma <ce.abhishek@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/11905
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: jihwan seo <jihwan.seo@samsung.com>
Reviewed-by: Madan Lanka <lanka.madan@samsung.com>
(cherry picked from commit 4815e501d2af69d9b19fd28e866134c61b0dd981)
Reviewed-on: https://gerrit.iotivity.org/gerrit/12119
Reviewed-by: Uze Choi <uzchoi@samsung.com>