EX-3640 test: mkdir on MDT0 in hot-pools.sh

EX-3640 test: mkdir on MDT0 in hot-pools.sh

To mkdir on MDT0 in hot-pools.sh by default, disable default LMV on
ROOT in init_hot_pools_env().

Test-Parameters: trivial mdscount=2 mdtcount=4 testlist=hot-pools.sh
Signed-off-by: Lai Siyao <lai.siyao@whamcloud.com>
Change-Id: Ie34b35a6d79fa4b0f2c1c5a58777cf6291cd8d27
Reviewed-on: https://review.whamcloud.com/44590
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Hongchao Zhang <hongchao@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>