[JIRA IOT-768] fixed to parsing message length for TCP

when message length of TCP has short size (0~12 size)
Parser of Receiver is working as wrong size

Change-Id: I0bfee2be03cb22a7bbb53c4d0f419381c8306fb5
Signed-off-by: jihwan.seo <jihwan.seo@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/3403Reviewed-by: Ashok Babu Channa <ashok.channa@samsung.com>
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Patrick Lankswert <patrick.lankswert@intel.com>
Signed-off-by: hyuna0213.jo <hyuna0213.jo@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/4583Reviewed-by: Uze Choi <uzchoi@samsung.com>
Tested-by: Uze Choi <uzchoi@samsung.com>

resource/csdk/connectivity/lib/libcoap-4.1.1/pdu.c

@@ -330,6 +330,9 @@ unsigned int coap_get_length_from_header(const unsigned char *header, coap_trans
     unsigned int length_field_data = 0;
     switch(transport)
     {
+        case coap_tcp:
+            length = header[0] >> 4;
+            break;
         case coap_tcp_8bit:
             length = header[1] + COAP_TCP_LENGTH_FIELD_8_BIT;
             break;