qemu-iotests: Filter qemu-io output in 025

Signed-off-by: NFam Zheng <famz@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/025

@@ -56,7 +56,7 @@ _check_test_img
 
 echo
 echo "=== Resizing image"
-$QEMU_IO "$TEST_IMG" <<EOF
+$QEMU_IO "$TEST_IMG" <<EOF | _filter_qemu_io
 length
 truncate $big_size
 length