LU-8788 tests: modify create_pool to use as wrapper

LU-8788 tests: modify create_pool to use as wrapper

Changed the required places which directly call lctl
pool_new command to use create_pool() wrapper.

Seagate-bug-id: MRP-2683
Signed-off-by: Jadhav Vikram <jadhav.vikram@seagate.com>
Change-Id: I83a867072ae289f820036338249182a3112e7fba
Reviewed-on: http://es-gerrit.xyus.xyratex.com:8080/11162
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/23541
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>