Code review comment for lp:~sylvain-pineau/checkbox/add_removable_attribute_to_udev_resource

I don't think we should do benchmarking on removable devices (yet; we may have to when we start testing USB 3.0). The reason is that this is very dependent on the device itself, I've seen USB sticks with transfer rates as low as 1 MB/s, especially cheap ones. On the other hand, performance for internal hard drives is pretty much standard so we *can* benchmark those more reliably.