LU-15506 tests: skip conf-sanity test_32b until fixed

LU-15506 tests: skip conf-sanity test_32b until fixed

The new disk2_10-ldiskfs and disk2_12-ldiskfs images are failing
conf-sanity test_32b.  Rather than remove the images themselves,
which are large and would consume more space in Gerrit if removed
and re-added, instead skip them until the test can be fixed/o

Test-Parameters: trivial testlist=conf-sanity env=ONLY=32
Fixes: f2143c0790bb ("LU-11643 tests: add new images and tests for upgrade tests")
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I5e6af27669773f67b16786aeffc24e995e3ebbe5
Reviewed-on: https://review.whamcloud.com/46403
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>