fedpkg: Remove filenames option from completion
    
    The bash completion 'filenames' option prevents proper completion of
    local refs like tmz/f13.
    
    On systems with bash-completion >= 1.2, this should have little effect
    because the _filedir command sets the option as needed (or emulates it
    on older bash releases that lack compopt).
    
    On systems with older bash-completion (like EL-5 currently), there is a
    minor downside in that filename completion won't append trailing slashes
    to directories without the 'filenames' option.  Ideally, bash-completion
    will be updated on EL-5 and this minor inconvenience will vanish
    sometime soon.