Change calling convenction of WAIT_Enter() to be sess agnostic

bin/varnishd/cache/cache_session.c

@@ -288,7 +288,7 @@ SES_Wait(struct sess *sp)
 	CHECK_OBJ_NOTNULL(sp, SESS_MAGIC);
 	pp = sp->sesspool;
 	CHECK_OBJ_NOTNULL(pp, SESSPOOL_MAGIC);
-	if (WAIT_Enter(pp->http1_waiter, sp)) {
+	if (WAIT_Enter(pp->http1_waiter, sp, sp->fd)) {
 		VSC_C_main->sess_pipe_overflow++;
 		SES_Delete(sp, SC_SESS_PIPE_OVERFLOW, NAN);
 	}

bin/varnishd/waiter/cache_waiter.c

@@ -74,11 +74,13 @@ WAIT_Init(waiter_handle_f *func)
 }
 
 int
-WAIT_Enter(const struct waiter *w, struct sess *sp)
+WAIT_Enter(const struct waiter *w, void *ptr, int fd)
 {
+	struct sess *sp;
 
 	CHECK_OBJ_NOTNULL(w, WAITER_MAGIC);
-	CHECK_OBJ_NOTNULL(sp, SESS_MAGIC);
+	CAST_OBJ_NOTNULL(sp, ptr, SESS_MAGIC);
+	assert(fd >= 0);
 	assert(sp->fd >= 0);
 
 	return (w->impl->pass(w->priv, sp));

bin/varnishd/waiter/waiter.h

@@ -50,7 +50,7 @@ struct waiter_impl {
 };
 
 /* cache_waiter.c */
-int WAIT_Enter(const struct waiter *, struct sess *sp);
+int WAIT_Enter(const struct waiter *, void *ptr, int fd);
 struct waiter *WAIT_Init(waiter_handle_f *);
 const char *WAIT_GetName(void);
 int WAIT_Write_Session(struct sess *sp, int fd);