vdc-manage allows setting non-existant hypervisor

[Metallion]

Problem

When modifying a host node's hypervisor, there is no check done to see if the hypervisor is valid.

vdc-manage>> host modify hn-hva1 --hypervisor hvm
vdc-manage>> host show
UUID     Node ID   Hypervisor  Architecture  Usage  Status  Scheduling
hn-hva1  hva.hva1  hvm         x86_64        0%     online  true

Solution

Add a check and fail if the hypervisor being set is invalid.

[Metallion]

These are the supported hypervisors. https://github.com/axsh/wakame-vdc/blob/develop/dcmgr/lib/dcmgr/constants/host_node.rb#L17

This is the line that doesn't seem to work. https://github.com/axsh/wakame-vdc/blob/develop/dcmgr/lib/dcmgr/cli/host.rb#L68-L70