LU-12775 test: reorder 'tar' command options

LU-12775 test: reorder 'tar' command options

'tar' in RHEL8 is stricter in command option order.

Test-Parameters: trivial \
envdefinitions=ONLY="32c" \
clientdistro=el8.1 serverdistro=el8.1 \
mdscount=2 mdtcount=4 testlist=conf-sanity

Signed-off-by: Lai Siyao <lai.siyao@whamcloud.com>
Change-Id: I814203808efae4a746166abd3ba08f2bc5fce8f7
Reviewed-on: https://review.whamcloud.com/36907
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Wei Liu <sarah@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>