Make all parsers use credentials

Summary:
We need to issue all commands as $repository->junk() so we can pick up
credentials. Some of this stuff predates that change landing.

(I removed the "https" vs "svn+ssh" fallback code since it's specific to
Facebook, affected a tiny number of commits, is basically an SVN bug with UTF-8
handling and HTTP support, and doesn't make sense in the general case. The user
has the tools they need to force it via "reparse.php" if it's really an issue.)

Test Plan: Created new authenticated-remote mercurial and git repositories and
pulled/discovered them with credentials.

Reviewers: Makinde, jungejason, nh, tuomaspelkonen, aran

Reviewed By: Makinde

CC: aran, Makinde

Differential Revision: 970