virhostdevtest: Don't leak @mgr->activeSCSIHostdevs

virhostdevtest: Don't leak @mgr->activeSCSIHostdevs

So the hostdev manager has some lists to keep track which devices
are active (=assigned to a domain) or inactive. The manager and
its lists are allocated in myInit and freed in myCleanup but one
of them (activeSCSIHostdevs) was missing. Also, the order in
which the cleanup was done doesn't make it easy to spot it,
therefore reoder it.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>