Non-modular kbus has no way to remove unused devices

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When kbus is built into the kernel, i.e. not as a module, there is (at present) 
no way to have it expire unused unloved devices. This leads to some test 
failures, which are expecting to be able to rmmod and have them go away.

We might fix this by having the RESET ioctl clean up and remove all but kbus0? 
I suppose it ought to require some sort of priviliges, e.g. current_uid()==0.

Original issue reported on code.google.com by [email protected] on 12 Jan 2011 at 4:55