mdns/fuzzer: Fix non-instrumentation test to reproduce fuzzer issues

Regression from 2893d7e21b skipped reading the packet causing issues when locally reproducing crashed found by the fuzzer


* Original commit: espressif/esp-idf@dae8033

components/mdns/test_afl_fuzz_host/test.c

@@ -205,6 +205,7 @@ int main(int argc, char** argv)
         // Note: parameter1 is a file (mangled packet) which caused the crash
         file = fopen(argv[1], "r");
         assert(file >= 0 );
+        len = fread(buf, 1, 1460, file);
         fclose(file);
     }