update mqttd program to compatble with android app

guowenxue

8 hours ago 489b6a3c10ccaff0fd0de55b5030e2992d122a7b

 project/4.mqttd/booster/logger.c

@@ -101,7 +101,7 @@
    {
        if ( !(fp = fopen(fname, "a+")) )
        {
            fprintf(stderr, "%s() failed: %s\n", __func__, strerror(errno));
            fprintf(stderr, "%s() %s failed: %s\n", __func__, fname, strerror(errno));
            return -2;
        }
        L.fp = fp;