added Node API tests

* fixed all tests
* coverage increased from 66.52% to
  75.39%

I'm not entirely sure that I mocked the baremetal stuff correctly, so if someone has 
a better/correct method, feel free to let me know.

The only untested items have to do with Alerts, FlavorTemplates, and Capacities; things we store in our local database.  I'm waiting for FlavorTemplates to make
it into tuskar before finishing tests for the latter two.