hash: Fix refcount type in HSH_DerefObjCore()

We want to avoid unsigned integers for reference counting since they
would hide underflows.

bin/varnishd/cache/cache_hash.c

@@ -981,7 +981,7 @@ HSH_DerefObjCore(struct worker *wrk, struct objcore **ocp, int rushmax)
 	struct objcore *oc;
 	struct objhead *oh;
 	struct rush rush;
-	unsigned r;
+	int r;
 
 	CHECK_OBJ_NOTNULL(wrk, WORKER_MAGIC);
 	TAKE_OBJ_NOTNULL(oc, ocp, OBJCORE_MAGIC);

bin/varnishd/cache/cache_req_body.c

@@ -269,7 +269,6 @@ VRB_Free(struct req *req)
 
 	r = HSH_DerefObjCore(req->wrk, &req->body_oc, 0);
 
-
 	// each busyobj may have gained a reference
 	assert (r <= req->restarts + 1);
 }