[IOT-994] Fixing crash for parsing arbitrary UTF-8 payload

[IOT-994] Fixing crash for parsing arbitrary UTF-8 payload

Avoid the crash by checking whether the cbortype is map.
Fundamentally, no-cbor type payload should be filtered in tinycbor library.
This change can be removed later.

Change-Id: Icde1422c61319d8c5e66675d9ef2b66f30dc4077
Signed-off-by: Markus Jung <markus.jung@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/7737
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Uze Choi <uzchoi@samsung.com>
Reviewed-by: Markus Jung <markus.jung85@gmail.com>