quorum: Clean up quorum_aio_get()

Make sure that all fields of the new QuorumAIOCB are zeroed when the
function returns even without explicitly setting them. This will protect
us when new fields are added, removes some explicit zero assignment and
makes the code a little nicer to read.
Suggested-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NAlberto Garcia <berto@igalia.com>

block/quorum.c

@@ -164,20 +164,17 @@ static QuorumAIOCB *quorum_aio_get(BlockDriverState *bs,
     QuorumAIOCB *acb = g_new(QuorumAIOCB, 1);
     int i;
 
-    acb->co = qemu_coroutine_self();
-    acb->bs = bs;
-    acb->offset = offset;
-    acb->bytes = bytes;
-    acb->qiov = qiov;
-    acb->qcrs = g_new0(QuorumChildRequest, s->num_children);
-    acb->count = 0;
-    acb->success_count = 0;
-    acb->rewrite_count = 0;
-    acb->votes.compare = quorum_sha256_compare;
-    QLIST_INIT(&acb->votes.vote_list);
-    acb->is_read = false;
-    acb->vote_ret = 0;
+    *acb = (QuorumAIOCB) {
+        .co                 = qemu_coroutine_self(),
+        .bs                 = bs,
+        .offset             = offset,
+        .bytes              = bytes,
+        .qiov               = qiov,
+        .votes.compare      = quorum_sha256_compare,
+        .votes.vote_list    = QLIST_HEAD_INITIALIZER(acb.votes.vote_list),
+    };
 
+    acb->qcrs = g_new0(QuorumChildRequest, s->num_children);
     for (i = 0; i < s->num_children; i++) {
         acb->qcrs[i].buf = NULL;
         acb->qcrs[i].ret = 0;