After discovering this page I did some experimentation; connecting and disconnecting my iPhone 4 (ios 7.1.2) with up-to-date Ubuntu Unity 16.04 running on a MacBookPro7,1
I found that just confirming Trust on the iPhone had no effect; { in fact I am asked repetitively to allow trust on this system but that is another matter }
I also found that usbmuxd is playing a big part in this problem, so forcing usbmuxd to exit is a quick and dirty fix.
/usr/sbin/usbmuxd -X After running the command I can charge the phone, and connect to it as a wireless or bluetooth hotspot without the cpu bandwidth consumption.
I hope this helps someone with more expertise than myself to find a more acceptable fix for this.
