ensure x-compute-request-id is added to response headers from nova v2 api

In commit:

https://github.com/openstack/nova/commit/49d83e356afd6197fc95277f0d18723bdfa11652

The addition of the x-compute-request-id to the response headers was moved out to a separate module.

In order to ensure that it gets added to response headers, some additional options are required in nova api-paste.ini
Merge pull request #584 from mancdaz/master-576

ensure x-compute-request-id is added to response headers from nova apiv2