TT#172650 use custom software ID string for cert CN

Change-Id: Ie52196bc492c9ad791b4a619410795e2dadbe1f0

daemon/dtls.c

@@ -241,8 +241,10 @@ static int cert_init(void) {
 
 	/* common name */
 
+	const char *cn = rtpe_config.software_id ?: "rtpengine";
+	size_t cn_len = MIN(strlen(cn), 63);
 	if (!X509_NAME_add_entry_by_NID(name, NID_commonName, MBSTRING_UTF8,
-				(unsigned char *) "rtpengine", -1, -1, 0))
+				(unsigned char *) cn, cn_len, -1, 0))
 		goto err;
 
 	if (!X509_set_subject_name(x509, name))