No metrics for some of the chassis states

[petshopjke1337]

Recently we started using ipmi_exporter and found out that there is no metrics for Drive Fault and Cooling/fan fault states

System Power : on
Power overload : false
Interlock : inactive
Power fault : false
Power control fault : false
Power restore policy : Restore
Last Power Event : unknown
Chassis intrusion : inactive
Front panel lockout : inactive
Drive Fault : false
Cooling/fan fault : false
Chassis Identify state : off
Power off button : enabled
Reset button : enabled
Diagnostic Interrupt button : enabled
Standby button : enabled
Power off button disable : unallowed
Reset button disable : unallowed
Diagnostic interrupt button disable : unallowed
Standby button disable : unallowed

[bitfehler]

Thanks for the patch!