LU-9024 tests: improve conf-sanity test_63 output

LU-9024 tests: improve conf-sanity test_63 output

Improve the output of conf-sanity.sh test_63 to fix SLES11
test failures caused by different /proc/slabinfo results.
Replace "ldisk" with "ldiskfs".

Load ldiskfs module on the MDS if test is run with ONLY=63.
Compute number of slab entries per page even if the slab
is using multiple pages to improve object efficiency.

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: I7424c797a5955c06d2107c2047d3e2b64749fa56
Reviewed-on: https://review.whamcloud.com/25880
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Minh Diep <minh.diep@intel.com>