qcow: Fix qcow1 exit fault

Even though qcow1 doesn't use the refcount table, the cleanup path still
attempts to iterate over its LRU list. Initialize the list to avoid a
segfault on exit.
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

disk/qcow.c

@@ -1437,6 +1437,7 @@ static struct disk_image *qcow1_probe(int fd, bool readonly)
 
 	l1t->root = (struct rb_root)RB_ROOT;
 	INIT_LIST_HEAD(&l1t->lru_list);
+	INIT_LIST_HEAD(&q->refcount_table.lru_list);
 
 	h = q->header = qcow1_read_header(fd);
 	if (!h)