LU-8687 tests: list pool on mds when mgs is separate

LU-8687 tests: list pool on mds when mgs is separate

In case of separate MGS and MDS setup list pool on MGS
will show nothing, so listing pool from MDS instead of
MGS.

Test-Parameters: testlist=conf-sanity,ost-pools

Seagate-bug-id: MRP-3327
Signed-off-by: Jadhav Vikram <jadhav.vikram@seagate.com>
Change-Id: If5e9e6a7303059ab79e14967d2ea86b6d61c8aba
Reviewed-on: http://es-gerrit.xyus.xyratex.com:8080/11895
Reviewed-by: Vladimir Saveliev <vladimir.saveliev@seagate.com>
Reviewed-by: Rahul Deshmukh <rahul.deshmukh@seagate.com>
Tested-by: Elena V. Gryaznova <elena.gryaznova@seagate.com>
Reviewed-on: https://review.whamcloud.com/23046
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Reviewed-by: Fan Yong <fan.yong@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>