added and updated tuskar API tests

* added Racks, ResourceClasses, and Flavors
  tests
* coverage increased from 53.22% to 66.52%
* updated tuskar test data to add pythonclient
  objects; fixed resulting issues
* re-ordered methods to put methods dealing with
  similar objects together
* added another node-related API test failure;
  these wil lbe dealt with in a subsequent patch