Since iRMC S6 2.00, iRMC firmware disables IPMI over LAN
with default iRMC firmware configuration.
To deal with this firmware incompatibility, this commit
modifies driver's methods which use IPMI to first try
IPMI and, if IPMI fails, try to use Redfish API.
Story: 2010396
Task: 46746
Change-Id: I1730279d2225f1248ecf7fe403a5e503b6c3ff87