add some tests for host and seperate negative ones

For host operation, there are some APIs: list, show, update, startup,
shutdown, reboot. This patch will mainly add some negative tests for
update, startup, shutdown, reboot. It is important to note that, for
Libvirt Driver currently, there are no implementations for
set_host_enabled/host_maintenance_mode/host_power_action.

Change-Id: Ia810b956a20eae67e8ec43e3edf9fcb019f71711
Merge "add some tests for host and seperate negative ones"