bmc (napalm_redfish.bmc:BmcDriver) reads a BMC over Redfish where it
answers. A BMC that refuses Redfish (no license) is read and switched over
IPMI. A getter that fails over Redfish is asked over IPMI where IPMI has it;
IPMI is opened only then. Power control goes over Redfish when it answers,
and a refusal is final. The BMC is reset over Redfish only. Same account
for both; ipmi_port in optional_args.
Discovery suggests bmc for a BMC it finds: the fingerprint rules moved from
RedfishDriver to BmcDriver.