Wrong user shown for deployments created with manual jobs

When manual job that creates deployment is run the user shown on Operations / Environments for the deployment is the one that initially created the job and not the one that run the job. See https://gitlab.com/gitlab-org/gitlab-ce/issues/56130#note_136129555.

The reason is that when Ci::PlayBuildService is executed we update the user for the job but not for the deployment. Not sure will there be any consequences if we update the deployment user too (one will be we'll lose track who created it).

One way to workaround this could be to expose the Ci::Build#user instead of the Deployment#user if these two are different (and maybe if the job has when: "manual" as additional check).