Have to run renku session login for every repo in order to start a session

[olevski]

To reproduce:

1. renku login https:dev.renku.ch
2. renku clone https://gitlab.dev.renku.ch/tasko.olevski/test-18.git
3. cd test-18
4. renku session start -p renkulab
5. You get the error message: Error: Please run the renku login command to authenticate with Renku.

But I have already logged into renku in step 1. This command then has to be rerun inside every repo after the repo has been cloned. The CLI should adjust the repo/config to include the credentials and not require users to re-login for every repo that is cloned.