LU-17450 test: disable test 56x 56xa 56xb in sanity

LU-17450 test: disable test 56x 56xa 56xb in sanity

Add the interop tests 56x, 56xa, 56xb into always_except before
the patch https://review.whamcloud.com/53997 in LU-17525 is landed.

Test-Parameters: trivial testlist=sanity
Signed-off-by: Hongchao Zhang <hongchao@whamcloud.com>
Change-Id: I99fa7be9dc7f50113d463aea4b321502b31d7348
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/54962
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Li Xi <lixi@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>