LU-16163 tests: skip racer_on_nfs for NFSv3

LU-16163 tests: skip racer_on_nfs for NFSv3

Export ALWAYS_EXCEPT env for child NFS test

Lustre-change: https://review.whamcloud.com/50579
Lustre-commit: 892d726f274c7cd4e505689ad69194ac68dc323b

Fixes: 513eb670b0 ("LU-16163 tests: skip racer_on_nfs for NFSv3")
Test-Parameters: trivial testlist=parallel-scale-nfsv3
Signed-off-by: Alex Deiter <adeiter@tintri.com>
Change-Id: Ibb4a9916166f13ab9bd2374b33d4313453972276
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/50801
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Minh Diep <mdiep@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>