t/dedupe: fix init of all thread variables

->dupes wasn't initialized, for instance. Just memset the
whole thing, so we don't run into this again.

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/t/dedupe.c b/t/dedupe.c
index b43b677..5b88fcb 100644
--- a/t/dedupe.c
+++ b/t/dedupe.c
@@ -387,10 +387,8 @@
 
 	threads = malloc(num_threads * sizeof(struct worker_thread));
 	for (i = 0; i < num_threads; i++) {
+		memset(&threads[i], 0, sizeof(struct worker_thread));
 		threads[i].fd = f->fd;
-		threads[i].items = 0;
-		threads[i].err = 0;
-		threads[i].done = 0;
 
 		err = pthread_create(&threads[i].thread, NULL, thread_fn, &threads[i]);
 		if (err) {