Drop PIDFile line from .service
    
    Redis is not running as a daemon and so it is not creatnig a pidfile -
    thus we need to remove the reference in the .service file.
    
    Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=973151
    Signed-off-by: Fabian Deutsch <fabiand@fedoraproject.org>