acc_radius: use snprintf() instead of sprintf()

src/modules/acc_radius/acc_radius_mod.c

@@ -361,7 +361,7 @@ int acc_radius_send_request(struct sip_msg *req, acc_info_t *inf)
 		tsecmicro = inf->env->tv.tv_sec
 					+ ((double)inf->env->tv.tv_usec / 1000000.0);
 		//radius client doesn t support double so convert it
-		sprintf(smicrosec, "%17.6f", tsecmicro);
+		snprintf(smicrosec, 18, "%17.6f", tsecmicro);
 		ADD_RAD_AVPAIR(RA_TIME_STAMP, &smicrosec, -1);
 	} else {
 		av_type = (uint32_t)inf->env->ts;