When a compute service fails, the power states of the hosted VMs are not
updated. A normal user querying his or her VMs does not get any indication
about the failure. Also there is no indication about maintenance.
This change will expose new attribute host_status to user querying his
VMs. Attribute is only seen if policy allows.
DocImpact: This adds API microversion
Implements blueprint get-valid-server-state
APIImpact
Change-Id: I5abea08bdc27624a7f23a7db8964f8c2a7b0eaa7