Working so far!
First, I don't think this is just a ML issue...has been happening to our MacBook Pro for more than a year! As with everyone else, it was the UBD process taking up most of my CPU %. I am not an expert, so not saying everyone should try this, but given the reported connection to iCloud, Game Center, etc., I tried a few things.
What I think worked was:
Went to system preferences and signed out of iCloud and confirmed deleting all iCloud info off my local Mac. Restarted iCloud and gave permission to Calendar, Mail, Contacts, Photostream, Find my Mac (things I use and sync b/w different Apple devices).
Having said that, prior to doing this, I had tried a few other solutions, so not sure if they may have played a role? Also, b/c I have several iDevices synced through iCloud, I'm not sure if this is what kept all my iCloud info intact, or if it would have remained even after deleting it off my MacBook? Maybe someone who knows more about iCloud can comment on that?
1)First thing I had tried was to: open keychan access and find the certificates com.apple.ubiquity.peer-uuid...I reset the privileges to allow always trust, which was mentioned in other threads. Rebooted...didn't seem to change anything.
2)Also had read about Game Center being and issue so dragged the application out to my desktop (it won't let you delete it). I think on reboot (but it may have done it before shutdown) OSX created a new version of it in applications, as it is a "needed" file. But no joy here either.
3) Signed out of iCloud as discussed at the beginning.
Within 10 minutes my CPU temp had dropped by 6 or 8 degrees Celcius! The fan is quiet. I have restarted all apps except Game Center (which I personally don't have much interest in) ie.- Calendar, Mail, Contacts, Photostream, Find my Mac.
Hope this helps,
SS