LU-16905 tests: Fix 'timeout' value under sanity-quota/18

LU-16905 tests: Fix 'timeout' value under sanity-quota/18

Presently timeout is picked up via sysctl command
under sanity-quota/18. Which is picking up timeout
from incorrect location. This patch fixes the issue
by reading via $LCTL directly.

sysctl output:
timeout=$(sysctl -n lustre.timeout)
sysctl: cannot stat /proc/sys/lustre/timeout: No such file or directory

Test-Parameters: trivial fstype=zfs testlist=sanity-quota env=ONLY=18
Signed-off-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Change-Id: I4604d31c615fa65bf79598cc09f05d9c7c7abf1b
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/51337
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Hongchao Zhang <hongchao@whamcloud.com>