Include documentation for hash_always_miss and hash_ignore_busy vcl v…

…ariables.

git-svn-id: http://www.varnish-cache.org/svn/branches/2.1@5423 d4fa192b-c00b-0410-8231-f00ffab90ce4

doc/sphinx/reference/vcl.rst

@@ -520,6 +520,12 @@ req.backend.healthy
 req.http.header
   The corresponding HTTP header.
 
+req.hash_always_miss
+  Force a cache miss for this request.
+
+req.hash_ignore_busy
+  Ignore any busy object during cache lookup.
+
 The following variables are available while preparing a backend
 request (either for a cache miss or for pass or pipe mode):