connector: Clean up GSimpleAsyncResult usage
connector: Clean up GSimpleAsyncResult usage

• Don't use the op_res at all. If the operation failed, we always set an
  error.
• Use _async functions as source tags, not _finish.
• Remove weird spooky action at a distance to change the tag based on
  priv->reg_op.
• Actually use a different source tag for _connect_async and
  _register_async.

freedesktop-unofficial-mirror/wocky,freedesktop-unofficial-mirror/wocky,noonien-d/wocky,noonien-d/wocky,freedesktop-unofficial-mirror/wocky,noonien-d/wocky