block/qcow2.c: call qcow2_free_snapshots in the function of qcow2_close

Signed-off-by: NLi Zhi Hui <zhihuili@linux.vnet.ibm.com>
Reviewed-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/qcow2.c

@@ -635,6 +635,7 @@ static void qcow2_close(BlockDriverState *bs)
     g_free(s->cluster_cache);
     qemu_vfree(s->cluster_data);
     qcow2_refcount_close(bs);
+    qcow2_free_snapshots(bs);
 }
 
 static void qcow2_invalidate_cache(BlockDriverState *bs)