Added checking the type of key to prevent crash
Added checking the type of key to prevent crash

If stack received crafted packet without string key,
it can occur crash in tinycbor like below code.
cbor_assert(cbor_value_is_byte_string(value) || cbor_value_is_text_string(value))

Change-Id: I1ac137ab475faa592dadcc426ff530bef2c7e6fd
Signed-off-by: Jaehong Jo <69db334b3f87f30654728856fde276b43c835fe5@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/26869
Tested-by: IoTivity Jenkins <6267f6022d49a8a37a7fe97da24aebfab797522c@iotivity.org>
Reviewed-by: Kishen Maloor <c62ddea3cd661a9268bff15f07fc2229cdc9ac02@intel.com>

iotivity/iotivity-constrained,iotivity/iotivity-constrained,iotivity/iotivity-constrained,iotivity/iotivity-constrained