Remove v3 xml API sample tests

This is a step toward removing XML support from the v3 compute API.
First, we need to remove all of the tests that would fail once we start
ripping out the real code.

Part of blueprint remove-v3-xml-api

Change-Id: Ie2c280d5ea1e6b8756535deb05982a92561552db
Merge "Remove v3 xml API sample tests"