LU-15175 tests: fix ldev tests

LU-15175 tests: fix ldev tests

generate_ldev_conf() and tests use this fn do not
work on setup with ost targets located not on 1 oss
and do not work on failover setup where
  <facet>_HOST != <facet>failover_HOST.

Fixes: 0f17fc82a89a ("LU-7060 ldev: Added MGS NID substitution to ldev")
Test-Parameters: trivial testlist=conf-sanity
Signed-off-by: Elena Gryaznova <elena.gryaznova@hpe.com>
HPE-bug-id: LUS-2495
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Change-Id: Ief38df0b1a0ffa37a8e7a4545a69a453d6dba7bd
Reviewed-on: https://review.whamcloud.com/45613
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Olaf Faaland-LLNL <faaland1@llnl.gov>
Reviewed-by: Oleg Drokin <green@whamcloud.com>