Change to name-only lookups in RAKP

In IPMI2, there are two modes the BMC can regard the Role parameter.
It can either consider it a 'max privilege' or 'match privilege'.
It defaulted to 'match privilege' in order to enhance compatibility
with some earlier BMC implementations that misinterpreted the
specification in a way that allowed 'match privilege' to work but
'max privilege' to break without a specific workaround for that BMC.
That BMC family is pretty much out of service and if the same issue
arises later, we can put in auto-detect and workaround pretty cheaply.
With this in mind, change the mode to look account up by name only
since that is how 99% of ipmitool invocations are done and it
also is a more straightforward model.

Change-Id: Ibf82b70e1b85e4e05c93365a684e21c434b4d5b4