The effect of this is that the root object in the binheap could be
wrong and thus hold the expiry thread hostage, even though other objects
were ripe for expiry. 

This would show up as inflated obj/objcore/objhdr counts, but have no
other deleritous effects.

Detected, conclusively, by:	sky


git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@5195 d4fa192b-c00b-0410-8231-f00ffab90ce4