Updating Confgit Url does not update Config Checkout

When updating the confgit-url config variable, the checkout folder used does not update the upstream URL.

This causes issues when updating access tokens on expiry, as the old token is held in the .git/config file of the confgit checkout.

Process of reproducing:

1. Create valid config for lorry2 pointing to a valid confgit repo
2. Run lorry2 so that it pulls the confgit repo
3. Revoke token used for confgit
4. Create new token for confgit
5. Modify lorry2 config to use new token
6. Restart lorry2
7. ---> Lorry2 will fail to restart due to confgit being unreadable

Note this was done in a docker compose setup, with an external volume for storing the confgit repo.