Eliminate the backend refcount, n_conn serves as refcount and is all

we need.

Send warm dynamic backends "COLD" event before deleting them.

bin/varnishd/cache/cache_backend.c

@@ -103,7 +103,6 @@ vbe_dir_getfd(struct worker *wrk, struct backend *bp, struct busyobj *bo)
 	AN(vc->addr);
 
 	Lck_Lock(&bp->mtx);
-	bp->refcount++;
 	bp->n_conn++;
 	bp->vsc->conn++;
 	Lck_Unlock(&bp->mtx);
@@ -330,7 +329,7 @@ vbe_panic(const struct director *d, struct vsb *vsb)
 	VSB_printf(vsb, "      health=%s, admin_health=%s",
 	    bp->healthy ? "healthy" : "sick", bp->admin_health);
 	VSB_printf(vsb, ", changed=%.1f\n", bp->health_changed);
-	VSB_printf(vsb, "      refcount = %d\n", bp->refcount);
+	VSB_printf(vsb, "      n_conn = %u\n", bp->n_conn);
 }
 
 /*--------------------------------------------------------------------*/

bin/varnishd/cache/cache_backend.h

@@ -52,7 +52,6 @@ struct backend {
 
 	VTAILQ_ENTRY(backend)	list;
 	VTAILQ_ENTRY(backend)	vcl_list;
-	int			refcount;
 	struct lock		mtx;
 
 	VRT_BACKEND_FIELDS()
@@ -129,4 +128,4 @@ void VBT_Wait(struct worker *, struct vbc *);
 
 /* cache_vcl.c */
 void VCL_AddBackend(struct vcl *, struct backend *);
-void VCL_DelBackend(const struct backend *);
+void VCL_DelBackend(struct backend *);

bin/varnishd/cache/cache_backend_cfg.c

@@ -70,13 +70,11 @@ VRT_new_backend(VRT_CTX, const struct vrt_backend *vrt)
 
 	CHECK_OBJ_NOTNULL(ctx, VRT_CTX_MAGIC);
 	CHECK_OBJ_NOTNULL(vrt, VRT_BACKEND_MAGIC);
-
 	assert(vrt->ipv4_suckaddr != NULL || vrt->ipv6_suckaddr != NULL);
 
 	vcl = ctx->vcl;
 	AN(vcl);
 	AN(vrt->vcl_name);
-	assert(vrt->ipv4_suckaddr != NULL || vrt->ipv6_suckaddr != NULL);
 
 	/* Create new backend */
 	ALLOC_OBJ(b, BACKEND_MAGIC);

bin/varnishd/cache/cache_vcl.c

@@ -205,7 +205,7 @@ VCL_AddBackend(struct vcl *vcl, struct backend *be)
 }
 
 void
-VCL_DelBackend(const struct backend *be)
+VCL_DelBackend(struct backend *be)
 {
 	struct vcl *vcl;
 
@@ -215,6 +215,8 @@ VCL_DelBackend(const struct backend *be)
 	Lck_Lock(&vcl_mtx);
 	VTAILQ_REMOVE(&vcl->backend_list, be, vcl_list);
 	Lck_Unlock(&vcl_mtx);
+	if (vcl->temp == vcl_temp_warm)
+		VBE_Event(be, VCL_EVENT_COLD);
 }
 
 static void