object on the LRU list, we may not be holding the last reference.

Fixes:	#634

Tip of hat to:	Matt Page for execellent diagnosis & patch.



git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@4516 d4fa192b-c00b-0410-8231-f00ffab90ce4