CA-61529: weaken pre-condition for Host.shutdown and Host.reboot
CA-61529: weaken pre-condition for Host.shutdown and Host.reboot

We now only insist on the host being disabled, and allow the shutdown sequence to run as if the user had typed "halt" or "reboot" at the console.

In particular a service VM can now use the Host.reboot/shutdown API even though it is still running itself.

Signed-off-by: David Scott <63c9eb0ea83039690fefa11afe17873ba8278a56@eu.citrix.com>

sharady/xcp-networkd,koushikcgit/xcp-rrdd,johnelse/xcp-rrdd,simonjbeaumont/xcp-rrdd,djs55/xcp-networkd,robhoes/squeezed,djs55/xcp-rrdd,simonjbeaumont/xcp-rrdd,sharady/xcp-networkd,djs55/xcp-rrdd,koushikcgit/xcp-rrdd,koushikcgit/xcp-networkd,djs55/squeezed,djs55/xcp-networkd,koushikcgit/xcp-rrdd,johnelse/xcp-rrdd,koushikcgit/xcp-networkd