WIP sync repo owner

we currently set the repo owner on push/pull_request events. this can be super confusing for people when debugging.

this pull request changes that to set the repo owner at user_sync time.

it also adds 30 seconds to the overall sync time though, so i guess we should first fix that before we merge :/

the offending change is that in order to set the owner we need to know the owner type, but the payloads that we get on user_sync do not contain the owner type but only `:login` and `:id`, here: https://github.com/travis-ci/travis-core/blob/97d0476b6b1661550bc45f64f307c0385f8cb5d1/lib/travis/github/services/sync_user/repository.rb#L37