Fix warnings in dlz_mysqldyn_mod.c

Fix warnings in dlz_mysqldyn_mod.c

    dlz_mysqldyn_mod.c: In function ‘dlz_findzonedb’:
    dlz_mysqldyn_mod.c:1079:73: warning: unused parameter ‘methods’ [-Wunused-parameter]
     1079 | dlz_findzonedb(void *dbdata, const char *name, dns_clientinfomethods_t *methods,
          |                                                ~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~
    dlz_mysqldyn_mod.c:1080:34: warning: unused parameter ‘clientinfo’ [-Wunused-parameter]
     1080 |                dns_clientinfo_t *clientinfo) {
          |                ~~~~~~~~~~~~~~~~~~^~~~~~~~~~
    dlz_mysqldyn_mod.c: In function ‘dlz_lookup’:
    dlz_mysqldyn_mod.c:1111:63: warning: unused parameter ‘methods’ [-Wunused-parameter]
     1111 |            dns_sdlzlookup_t *lookup, dns_clientinfomethods_t *methods,
          |                                      ~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~
    dlz_mysqldyn_mod.c: In function ‘build_query’:
    dlz_mysqldyn_mod.c:465:19: warning: pointer ‘item’ used after ‘free’ [-Wuse-after-free]
      465 |              item = DLZ_LIST_NEXT(item, link))
    dlz_mysqldyn_mod.c:470:17: note: call to ‘free’ here
      470 |                 free(item);
          |                 ^~~~~~~~~~