EX-4572 tests: fix setfattr stack_trap in init_hot_pools_env()

EX-4572 tests: fix setfattr stack_trap in init_hot_pools_env()

This patch fixes setfattr stack_trap in init_hot_pools_env() to
resolve the following error:

/usr/lib64/lustre/tests/test-framework.sh: line 2:
trusted.dmv=0xd00c......: command not found

Test-Parameters: trivial testlist=hot-pools
Test-Parameters: trivial mdscount=2 mdtcount=4 testlist=hot-pools

Fixes: 7ff7b9d8cf0 ("EX-3640 test: mkdir on MDT0 in hot-pools.sh")
Change-Id: Ia406a066455bd83c2199f96507a11b36aa80fea2
Signed-off-by: Jian Yu <yujian@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/46662
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexandre Ioffe <aioffe@ddn.com>
Reviewed-by: John L. Hammond <jhammond@whamcloud.com>
Reviewed-by: Lai Siyao <lai.siyao@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>