limit: Fix rate limit not reseting state correctly (#438)

tower-limit/src/rate/service.rs

@@ -1,5 +1,5 @@
 use super::{error::Error, future::ResponseFuture, Rate};
-use futures::{try_ready, Future, Poll};
+use futures::{Async, Future, Poll};
 use tokio_timer::{clock, Delay};
 use tower_service::Service;
 
@@ -65,7 +65,9 @@ where
         match self.state {
             State::Ready { .. } => return self.inner.poll_ready().map_err(Into::into),
             State::Limited(ref mut sleep) => {
-                try_ready!(sleep.poll());
+                if let Async::NotReady = sleep.poll()? {
+                    tracing::trace!("rate limited exceeded; sleeping.");
+                }
             }
         }
 
@@ -85,17 +87,13 @@ where
                 // If the period has elapsed, reset it.
                 if now >= until {
                     until = now + self.rate.per();
-                    let rem = self.rate.num();
-
-                    self.state = State::Ready { until, rem }
+                    rem = self.rate.num();
                 }
 
                 if rem > 1 {
                     rem -= 1;
                     self.state = State::Ready { until, rem };
                 } else {
-                    // The service is disabled until further notice
-                    tracing::trace!("rate limit exceeded, disabling service");
                     let sleep = Delay::new(until);
                     self.state = State::Limited(sleep);
                 }