Properly update refs so reset works

Calling `git fetch origin master` will update the `FETCH_HEAD` but not `refs/remotes/origin/master` so the subsequent `git reset --hard origin/master` does not reset to the fetched head.  Calling `git fetch origin` (without the refspec) updates both `FETCH_HEAD` and `refs/remotes/origin/master`.  So the following hard reset does what is expected.