LU-10406 tests: stop running sanity-lfsck 31c

sanity-lfsck is failing about half the time it is run.
Add sanity-lfsck test 31c to the ALWAYS_EXCEPT list until
we understand and fix the issue.

Test-Parameters: trivial
Signed-off-by: James Nunez <james.a.nunez@intel.com>
Change-Id: Iace77e1b1ea59971548497063974628be9e70733
Reviewed-on: https://review.whamcloud.com/30694


Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
(cherry picked from commit d645c722)
Reviewed-on: https://review.whamcloud.com/31935


Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>