Backport #11590
Unfortunately when the virtual session is released it requires that the
real session does not exist. This worked fine when sessions were only
saved at the end of request/response cycle however, now sessions are
saved proactively this does not hold.
The result is a caught panic in the logs during every log-in. This
panic has no significant side-effects but should not occur.
This PR marks the virtual session as released when released and updates
it if the same session is released again.
Signed-off-by: Andrew Thornton <art27@cantab.net>
1ae5435e41