Don't freak out if trying to close a socket that was already closed.

lib/roles/triproxy.js

@@ -34,8 +34,11 @@ module.exports = function(options) {
   log.info('PULL socket bound on', options.endpoints.pull)
 
   lifecycle.observe(function() {
-    pub.close()
-    dealer.close()
-    pull.close()
+    try {
+      pub.close()
+      dealer.close()
+      pull.close()
+    }
+    catch (err) {}
   })
 }