Add predictive failure for MegaCli based RAID
Add test cases
MegaCli : Assume battery state as faulty if not specified
arcconf : Ignore 'Invalid controller number' when arcconf is present but no raid is configured
Bad logic on battery state
Fix empty battery state
Implement PredictiveFailure on PDs for MegaCli. Merge PR #50
megacli: adjust  test for fixes. #50