LU-11749 tests: sanity-sec 23b exec commands on right node

LU-11749 tests: sanity-sec 23b exec commands on right node

In sanity-sec test 23b, make sure commands are executed on
client 1, then client 2.
Otherwise, ACL mapping cannot be correctly demonstrated.

This is a backported patch from:
Lustre-commit: 3c64d3310b7b46689b69091f512663bcb5aecdaf
Lustre-change: https://review.whamcloud.com/33846

Test-Parameters: trivial clientcount=2 envdefinitions=ONLY=23b testlist=sanity-sec,sanity-sec,sanity-sec,sanity-sec,sanity-sec,sanity-sec

Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: Iffa3946be149313af696907fa6c83a6ea58cb3f6
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Reviewed-by: Wei Liu <sarah@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/34623
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>