json: Fix memleak in native msging repl

* src/gpgme-json.c (native_messaging_repl): Free request and
response after each loop.

--
If we only accept once request we should not loop. If we loop
we should do it properly.

src/gpgme-json.c

@@ -3665,6 +3665,10 @@ native_messaging_repl (void)
           log_error ("error writing request: %s\n", gpg_strerror (err));
           break;
         }
+      xfree (response);
+      response = NULL;
+      xfree (request);
+      request = NULL;
     }
 
   xfree (response);