deploy-local: Initialize self.server_url early

• Initialize self.server_url in DeployLocal._load_config(), using the
  git_scheme configuration setting instead of hard-coded "http".

• Use self.server_url in DeployLocal._get_remote_overrides() instead
  of reconstructing most of the server URL.

---

Related MRs:

• !223 (merged)
• !222 (merged) (This MR)
• master