LU-14701 tests: wrong get[set]_osd_param() call

sanity-dom:sanityn:test_19 is always skipped because of
get_osd_param() is called incorrectly for DOM=yes.
For osd-* MDT device is to be used instead of default
  device=${2:-$FSNAME-OST*}

Fixes: a7625cd2f37a ("LU-3285 test: add Data-on-MDT tests and fixes")
Test-Parameters: trivial testlist=sanity-dom env=ONLY=sanityn
Test-Parameters: trivial testlist=sanityn env=ONLY=19
Signed-off-by: Elena Gryaznova <elena.gryaznova@hpe.com>
HPE-bug-id: LUS-9965
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Reviewed-by: Alexander Zarochentsev <alexander.zarochentsev@hpe.com>
Change-Id: I2bb9fc7fbaac966ea2254071e7ea82b963a93ad3
Reviewed-on: https://review.whamcloud.com/43774
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Mike Pershin <mpershin@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>