LU-12312 tests: stop running sanity-sec test 31

sanity-sec test 31 is failing a high percent of time
and the failure is not understood.  Let's stop running
this test, add the test to the ALWAYS_EXCEPT list, until
we have a fix for this issue.

Test-Parameters: trivial testlist=sanity-sec
Signed-off-by: James Nunez <jnunez@whamcloud.com>
Change-Id: I07c3cb1b5d12c920f78efb942460608c664000b3
Reviewed-on: https://review.whamcloud.com/38128
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>