LU-17368 tests: init the variables in correct order

LU-17368 tests: init the variables in correct order

recovery-scale-lib expects the CLIENTS set:
  NODES_TO_USE=${NODES_TO_USE:-$CLIENTS}

but this variable initialized later:
  init_logging() ->
    init_clients_lists () ->
      export CLIENTS=$(comma_list $clients)

This wrong order leads to empty NODES_TO_USE and
recovery-*-scale tests failed with:
   dd: ssh: Could not resolve hostname dd: Name or service not known

Test-Parameters: trivial env=SLOW=no,FAILURE_MODE=HARD \
    clientcount=4 mdtcount=1 mdscount=2 osscount=2 \
    austeroptions=-R failover=true iscsi=1 \
    testlist=recovery-mds-scale,recovery-oss-scale,recovery-random-scale

Fixes: 2c12b93ccb ("LU-9798 tests: split server recovery tests")
HPE-bug-id: LUS-12058
Signed-off-by: Elena Gryaznova <elena.gryaznova@hpe.com>
Change-Id: I3967c7cca7f480610defbeba09b9f5628f7085d3
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/53477
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: Vladimir Saveliev <vladimir.saveliev@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>