Remove string from URL in list_revoke_events()

The extra string is causing the self URL to be
"/OS-REVOKE/events/events" instead of just
"OS-REVOKE/events".

Change-Id: I3b4e53ffabee5156b2b82b5831cfe23e98527a3a
Closes-Bug: 1384457
Merge "Remove string from URL in list_revoke_events()"