device-manager: Keep track as to whether or not the user specifically renamed the device.
If the user has not (via our protocol extension) renamed a device, but it happens to now have
a different name (e.g. module-combine automatically updating the description for us or udev-db
getting better etc.) then make sure we update our cache with this updated version.
If the user has set a name, enforce it's use, even if the description is updated by some other
means (e.g. the user manually editing the proplist or another module doing it for them).