Set noggin default avatar to retro
    
    The default in noggin for the libravatar default avatar (i.e. the avatar
    that shows when a user hasnt set their avatar) is an autogenerated
    robot.
    
    However, the majority of other applications in Fedora Infra use the
    "retro" avatar option. This changes the config of noggin in Fedora
    Accounts to use the retro option, rather than the robot one.
    
    Signed-off-by: Ryan Lerch <rlerch@redhat.com>