LU-16641 tests: fix sanity-quota_12b

LU-16641 tests: fix sanity-quota_12b

Fix sanity-quota_12b to don't fail after
creating $ilimit files with the same inode
hardlmit. It is a legal case to fail create
2048 files when inode hard limit is also 2048.

Lustre-change: https://review.whamcloud.com/53969
Lustre-commit: 25896b8b88207e181eba4994323865cce9878800

Test-Parameters: trivial fstype=zfs \
  env=ONLY=12b,ONLY_REPEAT=100 testlist=sanity-quota

Signed-off-by: Sergey Cheremencev <scherementsev@ddn.com>
Change-Id: Iea2e976ad1954dc2489ffa81e92e624364343069
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>