Emails gone after student view

If instructor has permission to view email addresses, but student has not, the email addresses are not shown for the instructor if a student has been viewing the roster.

Some caching issue as the emails come back after a while (minutes).

Probably fails in 12 too.

Steps to reproduce:

• Set permissions: instructor can view email, student can not view email
• As instructor, reset tool and the emails are listed
• As student, reset tool and the emails are not listed and the header 'email' is not listed
• As instructor, reset tool and the emails are gone. The header 'email' is still there though

I have tested this on https://trunk-mysql.nightly.sakaiproject.org and on our 11.4, with a separate browser for each role.