Move to oslo.middlware request_id module

The oslo-incubator request_id module has been deprecated and
removed for kilo, replaced by the request_id from oslo.middleware.

Note that we need to leave the oslo-incubator request_id shim in place
until after Kilo ships, so operators get fair warning about the
backwards-incompatible paste.ini change.

Change-Id: Iedbfede6d57312f565cf4b1ccb71a8418fad8620
Partial-Bug: #1380629
Merge "Move to oslo.middlware request_id module"