Fix bug in H1 session cleanup.
Fix bug in H1 session cleanup.

(Yes, obviously I managed to break 5.1 with my last commit before
the tag...)

feld/Varnish-Cache,feld/Varnish-Cache,gquintard/Varnish-Cache,feld/Varnish-Cache,gquintard/Varnish-Cache,feld/Varnish-Cache,gquintard/Varnish-Cache,feld/Varnish-Cache,gquintard/Varnish-Cache