Fixes #5640: Specify default user name and email when initializing confi...

...guration-repository

Ticket: http://www.rudder-project.org/redmine/issues/5640

To be merged in master
It is not run every time, only when the repository is first created.

But you raise an interesting point: if the git version is upgraded post-repository creation, these values will be missing.

I'm changing this.