always queue service stop if node shuts down

always queue service stop if node shuts down

Commit 61ae38eb6fc5ab351fb61f2323776819e20538b7 which ensured that
services get freezed on a node reboot had a side effect where running
services did not get gracefully shutdown on node reboot.
This may lead to data loss as the services then get hard killed, or
they may even prevent a node reboot because a storage cannot get
unmounted as a service still access it.

This commits addresses this issue but does not changes behavior of
the freeze logic for now, but we should evaluate if a freeze makes
really sense here or at least make it configurable.

The changed regression test is a result of the fact that we did not
adapt the correct behavior for the is_node_shutdown command in the
problematic commit. The simulation envrionment returned true
everytime a node shutdown (reboot and poweroff) and the real world
environment just returned true if a poweroff happened but not on a
reboot.

Now the simulation acts the same way as the real environment.
Further I moved the simulation implemenentation to the base class so
that both simulator and regression test system behave the same.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>