Add git_update_remote_branch to functions.

When $RECLONE=yes, and the branch specified for a project in stackrc is
a remote branch, the git_clone function would not recognize it as a
branch.  git_clone now attempts to recognize a remote branch and handle
it appropriately.

Change-Id: Ie23ff12eb5a7905088a9c2bb0ea2b02453ec0258
diff --git a/AUTHORS b/AUTHORS
index 4f771ce..22d5f32 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -1,6 +1,7 @@
 Aaron Lee <aaron.lee@rackspace.com>
 Aaron Rosen <arosen@nicira.com>
 Adam Gandelman <adamg@canonical.com>
+Andrew Laski <andrew.laski@rackspace.com>
 Andy Smith <github@anarkystic.com>
 Anthony Young <sleepsonthefloor@gmail.com>
 Armando Migliaccio <armando.migliaccio@eu.citrix.com>