LU-18105 tests: take care of "run LFSCK" message in dmesg

LU-18105 tests: take care of "run LFSCK" message in dmesg

"logging isn't available, run LFSCKn" message may get hidden due to
console rate limit feature which causes sanity.sh:test_818 to fail.

Set console_ratelimit to 0 for the duration of sanity.sh:test_818
execution.

HPE-bug-id: LUS-11913
Fixes: 44a359caae ("LU-15166 tests: restore osp-syn threads after test_818")
Test-Parameters: testlist=sanity env=ONLY=818,ONLY_REPEAT=20
Signed-off-by: Vladimir Saveliev <vladimir.saveliev@hpe.com>
Change-Id: Ibe5c254bebe28f65d37f279802944fff5894f981
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/55932
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Elena <elena.gryaznova@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>