Fix resource pool bug

And remove unnecessary named let.

knots/resource-pool.scm

@@ -1317,8 +1317,9 @@ available.  Return the resource once PROC has returned."
                                            start-time)
                                      'timeout)
                                  response))
-                           'timeout)))))
+                           'timeout))
-             (let loop ((reply (make-channel)))
+                     'timeout)))
+             (let ((reply (make-channel)))
                (put-message channel
                             (list 'checkout
                                   reply