Set correctly request parameters for the list_resources request
Set correctly request parameters for the list_resources request

The Neutron API requires that the content_type and accept headers
are correcty set in the request. This commit permit to fix this
issue.

It has been successfully tested with Tox.

Closes-Bug: 1754096

Change-Id: I977f97cd0692a86bac1d817fa1c4de27889f2675

stackforge/ooi,openstack/ooi