title: sessionReachabilityDidChange not called on watch
body: <p>I would like to have my watch app respond to the parent app on the phone being killed. When the watch app is running and the phone app is killed I get no callback from either <code>sessionReachabilityDidChange</code> or <code>sessionWatchStateDidChange</code>. Based on apple documentation: </p>
  
  <blockquote>
    <p>This method is called to let the current process know that its
    counterpart session’s reachability changed.</p>
  </blockquote>
  
  <p>So, it seems that I should get a callback. I've set the WCSession delegate to my class on the watch. The session on the watch receives callbacks for application context. Why am i not getting a reachability callback?</p>
  
  <p>Code Below..</p>
  
  <pre><code>+ (SomeClass *)sharedInstance {
      static dispatch_once_t pred;
      static SomeClass *shared = nil;
      dispatch_once(&amp;pred, ^{
          shared = [[SomeClass alloc] init];
          [Model sharedInstance].delegate = shared;
      });
      return shared;
  }
  
  #pragma mark - setup
  
  - (void)initializeSession {
      if ([WCSession isSupported]) {
          WCSession *session = [WCSession defaultSession];
          session.delegate = self;
          [session activateSession];
          [self sync];
      }
  }
  
  -(BOOL) hasValidWCSession {
      return ([WCSession isSupported] &amp;&amp; [WCSession defaultSession].isReachable);
  }
  
  
  #pragma mark - WCSessionDelegate
  
  - (void)session:(nonnull WCSession *)session didReceiveApplicationContext:(nonnull NSDictionary&lt;NSString *, id&gt; *)applicationContext {
  
      NSLog(@"application context received on watch: %@", applicationContext);
      [[Model sharedInstance] process:applicationContext];
  }
  
  
  - (void)sessionWatchStateDidChange:(WCSession *)session {
      NSLog(@"wcession state changed on watch");
  }
  
  - (void)sessionReachabilityDidChange:(WCSession *)session {
      NSLog(@"wcsession reachability changed on watch");
  }
  </code></pre>