LU-11785 tests: fix conf-sanity/98 mount check on 64K page

LU-11785 tests: fix conf-sanity/98 mount check on 64K page

This patch fix the mount option length check expectation
fail on 64K page. Since the maxopt_len is the minmium
value of page_size or 64K page_size, but the test cases
only hard code the length of option to the 4K one. This
patch add the mount options according to the page size.

Test-Parameters: trivial testlist=conf-sanity env=ONLY=98
Test-Parameters: testlist=conf-sanity env=ONLY=98 clientarch=aarch64 clientdistro=el8.6
Signed-off-by: Kevin Zhao <kevin.zhao@linaro.org>
Change-Id: Icdeb8b73308056e216c3f4ce71907b0c928d2c30
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/48177
Tested-by: Maloo <maloo@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: xinliang <xinliang.liu@linaro.org>