Adding new test cases for zone export showfile API

    1) "test_show_exported_zonefile_impersonate_another_project"
       Admin user is able to impersonate another project
       and to "show" created by tenant exports.
       Note: based on: 'x-auth-sudo-project-id' HTTP header.

    2) "test_show_exported_zonefile_all_projects"
       Use admin client to show zone export file of
       all tenants.
       Note: based on: "x-auth-all-projects" HTTP header.

    3) "test_show_exported_zonefile_any_mime_type"
       Validate that 200 OK and Content-Type: text/dns
       is received when client.
       sends "Accept: */*".

    4) "test_missing_accept_headers"
       Client request is missing Accept header.
       The header will be send with empty dict.
       Expected: {Content-Type: text/dns}

    5) "test_show_zonefile_using_not_existing_zone_export_id"
       "404 Not Found" is expected when not existing
       ID is used by client.

    6)"test_show_zonefile_not_supported_accept_value"
      Client sends 'Accept':'image/jpeg' for ShowZoneFile API.
      Expected: 406 Not Acceptable.

Change-Id: I8aa5dfe12781f21b9f41e0df19afb0e46eab31d8
3 files changed