EX-6170 tests: make sanity-lipe-scan3.sh support remote MDS

EX-6170 tests: make sanity-lipe-scan3.sh support remote MDS

The sanity-lipe-scan3.sh script was written to only run on a local
client+MDS configuration. This patch fixes it to support running
the lipe_scan3 command on remote MDS.

Test-Parameters: trivial testlist=sanity-lipe-scan3
Test-Parameters: trivial mdscount=2 mdtcount=4 \
testlist=sanity-lipe-scan3

Signed-off-by: Jian Yu <yujian@whamcloud.com>
Change-Id: I0ede3420c6f529cdfb9e97a5664945a5c2f0ff09
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/49559
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>