LU-10052 test: relate fs_log_size to recordsize

LU-10052 test: relate fs_log_size to recordsize

If the backend filesystem is ZFS, the block usage difference is
related to the recordsize of it, the maximum difference are 2 blocks.
This affects several different tests that have intermittent failures.

    replay-dual test_14b, replay-single test_20b, test_89

Change-Id: I36b184587306bd2b9221e5771bf1adfe071653ca
Signed-off-by: Hongchao Zhang <hongchao.zhang@intel.com>
Reviewed-on: https://review.whamcloud.com/30916
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Reviewed-by: James Nunez <james.a.nunez@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>