LU-14294 tests: fixed NFS configuration issue

LU-14294 tests: fixed NFS configuration issue

* Used the systemctl command to manage system services
* Used the same order of parameters to setup and cleanup NFS
* Used tab for indentation

Lustre-change: https://review.whamcloud.com/49062
Lustre-commit: 1a8fe55b17ac2bc2195aaba446467ccdac67b564

Test-Parameters: trivial clientdistro=el7.9 \
testlist=parallel-scale-nfsv3,parallel-scale-nfsv4
Test-Parameters: clientdistro=el8.7 \
testlist=parallel-scale-nfsv3,parallel-scale-nfsv4
Test-Parameters: clientdistro=el9.0 \
testlist=parallel-scale-nfsv3,parallel-scale-nfsv4
Test-Parameters: clientdistro=sles12sp5 \
testlist=parallel-scale-nfsv3,parallel-scale-nfsv4
Test-Parameters: clientdistro=sles15sp4 \
testlist=parallel-scale-nfsv3,parallel-scale-nfsv4
Test-Parameters: clientdistro=ubuntu2004 \
testlist=parallel-scale-nfsv3,parallel-scale-nfsv4

Change-Id: I6b087035ac7524aa99c0facad48f8c3fb7444cbc
Signed-off-by: Alex Deiter <adeiter@tintri.com>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/51283
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>