but also give it a return value since we don't have a cli in VCL.

However, I'm not sure how we will report the error in VCL, so still
log the trouble in shmlog.



git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@2751 d4fa192b-c00b-0410-8231-f00ffab90ce4