Under what circumstances would you hold an ACE inhibitor or ARB prior to surgery in a patient with CKD?  

Only if potassium is high or the patient is hypotensive.

I suppose if it was a high risk for hypotension or fluid shift, I may hold it. I'd rather be a bit hypertensive than under-perfused. If they are being used for reno protection, getting off them for a short period will have no influence.