LU-16163 tests: skip racer_on_nfs for NFSv3

LU-16163 tests: skip racer_on_nfs for NFSv3

This test is continually failing and nobody is available to
fix it (it may be an NFS bug or a Lustre bug, unsure).

This same test passes on NFSv4 regularly.

Lustre-change: https://review.whamcloud.com/50385
Lustre-commit: 513eb670b01f15104cbeb2909a141d2174dcc874

Test-Parameters: trivial testlist=parallel-scale-nfsv3
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I7d9ac390c26aa8478dd35457ba20061747c2b92e
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/50461
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>