update rubyipmi to 0.8.1 (RPM)

http://koji.katello.org/koji/taskinfo?taskID=177197 el6
http://koji.katello.org/koji/taskinfo?taskID=177201 el7
http://koji.katello.org/koji/taskinfo?taskID=177207 f19

As I don't have access to IPMI hardware at the moment, it should be tested if everything still works... @ohadlevy maybe?