LU-12100 tests: Use least qunit to set limit

LU-12100 tests: Use least qunit to set limit

Use least qunit to set lower limit for inodes in sanity-quota/2
This ensures that the limit is set at or above the minimum size.

Lustre-change: https://review.whamcloud.com/36797
Lustre-commit: 33e500cfb33406b8dddac46e1dfb5a3d59ff01c5

Test-Parameters: trivial
Test-Parameters: env=ONLY=2 testlist=sanity-quota
Test-Parameters: env=ONLY=2 testlist=sanity-quota fstype=zfs
Test-Parameters: env=ONLY=2,ONLY_REPEAT=20 fstype=zfs testlist=sanity-quota
Test-Parameters: mdtcount=2 mdscount=4 env=ONLY=2,ONLY_REPEAT=20 fstype=zfs testlist=sanity-quota

Signed-off-by: Nathaniel Clark <nclark@whamcloud.com>
Change-Id: I80e2c3cb66870d11f74f34c435e266a46630479b
Reviewed-on: https://review.whamcloud.com/36797
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: Olaf Faaland-LLNL <faaland1@llnl.gov>
Reviewed-on: https://review.whamcloud.com/38769
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>