Revert "Remove tripleo from nodepool config"

This reverts commit c982db10ffca4206a1c3f496fbe59a23bb1bac15.

We now have a) fixed nodepool to be less affected by outages, b)
restored the tripleo cloud to service and c) added a new pipeline to
make outages affect other people less.

Change-Id: I99972b8cae537bea259abb835ed12c3405df5e85