LU-15445 tests: sanity test_160p() fix

LU-15445 tests: sanity test_160p() fix

start() requires 2nd parameter device.
If start() is called without the 2nd parameter - the
empty mds1_dev is exported:
        eval export ${dev_alias}_dev=${device}
and test fails on failover setup with:
  CMD: lm0301 loop_dev=$(losetup -j  | cut -d : -f 1);
  lm0301: losetup: option requires an argument -- 'j'
dm_create_dev()
  local real_dev=<empty>
        -> setup_loop_device $facet <empty>
To reproduce the failure just run:
  ONLY=160p sh sanity.sh
on failover setup where mds1_HOST != mds1failover_HOST.

Fixes: c7d8fe3106 ("LU-14731 mdd: clear orphans changelog entries")
Test-Parameters: trivial env=ONLY="160p" testlist=sanity
Signed-off-by: Elena Gryaznova <elena.gryaznova@hpe.com>
HPE-bug-id: LUS-10674
Reviewed-by: Vladimir Saveliev <vlaidimir.saveliev@hpe.com>
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Change-Id: I2661567672aa9c6e23b5f17500d81053cf9c9fdd
Reviewed-on: https://review.whamcloud.com/46073
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>