maas-test should verify the BMC can be used for secure token exchange

[Mark Shuttleworth]

The patch attached checks the BMC to see if it correctly allows for the OS name, and primary OS name, to be written with bmc-device and read with bmc-info. If so, this might form the basis of a secure token exchange mechanism, where a token is written to the BMC by MAAS before PXE boot, and returned to MAAS by the booted system as a token of authenticity.

This presumes the connection to the BMC is secure and there are no insecure BMC user identities that might read the token. But if the BMC is not secure you have bigger problems in life than this :)

The patch will not apply cleanly, I had to rip code from maas-test into a small test harness to iterate quickly, but hopefully it's obvious how to integrate this.