Verify the response attributes of 'startup_host' API

This patch verifies the response attributes of 'startup_host' API.
The response body format of v2:
{
    "host": "57f5de2fa5b44f14974a4f50b9ffcbf8",
    "power_action": "startup"
}

The response body format of v3:
{
    "host": {
        "host": "4b392b27930343bbaa27fd5d8328a564",
        "power_action": "startup"
    }
}

Partially implements blueprint nova-api-attribute-test
Change-Id: If73daa85c374ce2ae8187cdc7f4929c8647ebe66
4 files changed