[ipad] Log out of proxy / clear cached credentials?

[MacHammer]

We are testing the use of the Global HTTP proxy option for devices going home with students. iPads are running 9.1. We are using Lightspeed, and the proxy policy and certificate are pushed by Meraki (legacy). Now that were are on 9, almost everything is working properly. However, I cannot figure out how to log out of the proxy and/or clear the cached credentials. As part of the check-in process when they return, I want to ensure that the students are logged out and ready for the next student. I believe the Lightspeed is set to an 8 hour timeout which is being enforced correctly. I tried using http://lsaccess.me/logout - that says the log out was successful, but blocked pages still show the same user and I'm never prompted for credentials. Does anyone have any ideas? Is there another lsaccess.me address I should be using?