Updated from global requirements

Change-Id: I575fcd39422dda9f9438cba5d4d4f71bc3f2ddda
Remove unnecessary json dumps/loads from tests

Tests used json dumps/loads to make sure each one will have a
separate copy of test data instead of pointer to original one.
Refactored this so now we have utility methods that return new
instance of test data each time.

Change-Id: I2306ba120fd61ede47e2762d910e004e66d6ce7f
Fix API inconsistence when changing node's states

When the request to change the power state is accepted by the server
(HTTP 202) it shouldn't return any response message, just like the
request to change the provision state. In the future after WSME add
the support to edit the Header Location, we should include a link to
the /nodes/<uuid>/states subresource so that clients know how to
track the status of the request, there's a FIXME in the code
mentioning that already.

The patch also add a check to the provision_state tests to make sure
the response body has no content.

Change-Id: I4fb1cd5c226cee2f9e0977e83cf2ffa7786b3b4a
Closes-Bug: #1270160
Merge "Updated from global requirements"
Merge "Remove unnecessary json dumps/loads from tests"
Merge "Fix API inconsistence when changing node's states"