Includes:
* Return a location in HTTP response header for PUT
/nodes/<node>/traits/<trait>.
* Correct order of arguments to assertEqual() in conductor manager unit
tests for traits.
* Use () rather than \ for multiline formatting.
* Set tags and traits fields on NodeModel to default of [] in DB node
create after DB insert.
Change-Id: Ia88f7ca69b777b82caca2871e44edab39f2a8310
Partial-Bug: #1722194
ccf22acb53