[6.0] 14be7fce0 add a lookup enum never to escape HSH_Lookup

[Dridi Boukelmoune]

commit 14be7fce0a4959a1b1ad24383cd944f7834ce348
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Mon Dec 3 22:49:51 2018 +0100

    add a lookup enum never to escape HSH_Lookup
    
    This is caught by
    
            assert(lr == HSH_HIT || lr == HSH_GRACE);
    
    in cnt_lookup()

diff --git a/bin/varnishd/hash/hash_slinger.h b/bin/varnishd/hash/hash_slinger.h
index 9434ce874..6c17b8374 100644
--- a/bin/varnishd/hash/hash_slinger.h
+++ b/bin/varnishd/hash/hash_slinger.h
@@ -50,6 +50,7 @@ struct hash_slinger {
 };
 
 enum lookup_e {
+	HSH_CONTINUE,
 	HSH_MISS,
 	HSH_BUSY,
 	HSH_HIT,