xenapi: virt unrescue method now supports objects

Commit 65ad230af5ece020822fa963dd30fd641a54ae91 ensured
that the compute API and manager are now getting objects
for the unrescue method.

This patch adds support to the virt driver code.

Change-Id: Ie6b587d3f89202a6987291bfaea88290241651f2
Add API schema for v2.1/v3 hosts API

By defining the API schema, it is possible to separate the validation
code from the API method. The API method can be more simple.
In addition, a response of API validation error can be consistent for
whole of Nova APIs.

Partially implements blueprint v3-api-schema

Change-Id: Ie252dce67f8e9d3292d8dad767b6113f7affcffd
vmware: VM diagnostics (v3 API only)

There is no formal definition for the VM diagnostics. For the
V2 API the diagnostics will be returned as they are today.

This will support backward compatibility with the existing API's.

Part of the blueprint v3-diagnostics

DocImpact

Change-Id: I6465ee6fc2edac0107e260297d9647c8a16b09ae
Merge "Add API schema for v2.1/v3 hosts API"
Merge "xenapi: virt unrescue method now supports objects"
Merge "vmware: VM diagnostics (v3 API only)"