Rebase not working with forked projects in 9.4.2

Following https://gitlab.com/gitlab-org/gitlab-ee/issues/2979. Steps to reproduce (@arihantar can you verify this?):

1. Create a new project.
2. Add a * as a protected branch.
3. Fork that project.
4. Attempt to create a MR and rebase.
5. The githost.log shows that the rebase failed due to the protected branch.

I see that RebaseWorker attempts to push to the target project, instead of the source project. Is that happening in all cases?

ZenDesk: https://gitlab.zendesk.com/agent/tickets/80795

/cc: @smcgivern