DELETE on action should not require Accept header

[benfrancis]

A cancelaction operation in the HTTP Basic Profile has the following requirements for a request:

• Method set to DELETE
• URL set to the URL of the ActionStatus resource

Currently this is supported, but it only works if the client sets an Accept header with the value application/json.

If the Accept header is not included the request gets routed to the wrong place by the content negotiation middleware and provides an error response with an HTML payload. The request should not require an Accept header because it does not expect a body in the response.

The fix might require modifying the content negotiation middleware to default to JSON rather than HTML.