[Zed] Set service_user_id from keystone relation

[rodrigogansobarbieri]

This is necessary so we can avoid ambiguities (by using the id vs name) when we want to use the service user.

(cherry picked from commit f7e65d27b1f93fe00bca13ed3ce741dce3eb9101) (cherry picked from commit 2320efdf793de0cea35fcedd531096e051e970a2) (cherry picked from commit 7e325def4558c8aea05a215062bd3b8dda7c518f)