Log project repository storage

What does this MR do and why?

When Rails receives git requests, log the storage name it's trying to reach using project.repository_storage. As per #418901 (comment 1481550761).

Contributes to #418901 (closed).

How to set up and validate locally

1. Open gitlab-development-kit/gitlab/log/development_json.log.
2. Clone a GDK project, for example git clone http://gdk.test:3000/gitlab-org/gitlab-test.git.
3. Confirm in development_json.log that there is now a log of "repository_storage":"default" for entries relating to "Repositories::GitHttpController".

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #418901 (closed)