Look at local and remote branches separately
    
    When running in a user clone of a dist-git repo, we want to check if
    the *remote* branch can be deleted:
    $ fedpkg clone foo
    $ cd foo
    $ .../distgit-commit-unused.py origin/f32
    
    In that case we only check if origin/f32 is contained any remote branch.
    
    When run by releng, I expect that this will be run locally, so
    $ cd .../foo
    $ .../distgit-commit-unused.py f32
    
    In that case, there should be no remote branches, but even if there
    were, we do not care about them.