Added passing of username and password to GitClient object during check_repository.
Review Request #7866 — Created Jan. 15, 2016 and submitted
* This means that a git URL with, inline authentication, can be created for performing the ls-remote command for checking whether a repository is valid.
Tool: Pyflakes Processed Files: reviewboard/scmtools/git.py Tool: PEP8 Style Checker Processed Files: reviewboard/scmtools/git.py