Bulk Data status operation should return 404 after delete

[dehall]

Describe the bug
After deleting a bulk data export, the server will respond to the status endpoint with a HTTP 202 and a status header describing the export as cancelled. Per the spec, it should instead return HTTP 404 not found.

From https://build.fhir.org/ig/HL7/bulk-data/export.html#bulk-data-delete-request

Following the delete request, when subsequent requests are made to the polling location, the server SHALL return a 404 Not Found error and an associated FHIR OperationOutcome in JSON format.

To Reproduce
Steps to reproduce the behavior:

1. Run a HAPI 7.0 server
2. Initiate a bulk data export at either [fhir base]/Patient/$export , [fhir base]/Group/[id]/$export, or [fhir base]/$export
3. Note the Content-Location header in the response
4. Issue an HTTP DELETE at that location
5. GET that location - the response will be a 202

This can also be seen with the Inferno Bulk Data test kit pointing to a HAPI server: https://github.com/inferno-framework/bulk-data-test-kit

Expected behavior
Response should be HTTP 404 not 202

Environment (please complete the following information):

• HAPI FHIR Version 7.0.2
• OS: n/a
• Browser n/a