Relax the same-origin check in the Git commit discovery daemon

Summary:
Git accepts either "git@x:/path" or "ssh://git@x.com/path" URIs to mean the
exact same thing, which is causing some false positives and confusion,
particularly because we sometimes mutate URIs.

Since this is just a sanity check, we don't really care about the username,
domain or credentials -- matching the paths is good enough. We're just trying to
make it hard to shoot yourself in the foot by copy-pasting the same local path
into two repositories and forgetting to change one, like I did. :P

Relax the check to only verify the paths are the same.

Test Plan:

• Ran unit tests, which should fully cover things.
• Ran commit discovery daemon in debug mode on incorrectly and correctly

configured repositories.

Reviewers: ajtrichards, jungejason, btrahan

Reviewed By: jungejason

CC: aran, jungejason

Maniphest Tasks: T710

Differential Revision: https://secure.phabricator.com/D1279