LU-18274 tests: reboot the not up nodes only

LU-18274 tests: reboot the not up nodes only

It is reasonable to reboot only those nodes which are
not up after previous reboot attempt.

Test-Parameters: trivial
Signed-off-by: Elena Gryaznova <elena.gryaznova@hpe.com>
HPE-bug-id: LUS-12442
Reviewed-by: Vladimir Saveliev <vladimir.saveliev@hpe.com>
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Change-Id: I3e1181f10bdf8b7e74ab532bd2e77d092dcf1c9b
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/56515
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>