Unify socket closers. Don't put them all in one try-catch or some might remain.

lib/units/triproxy/index.js

@@ -34,11 +34,13 @@ module.exports = function(options) {
   log.info('PULL socket bound on', options.endpoints.pull)
 
   lifecycle.observe(function() {
-    try {
-      pub.close()
-      dealer.close()
-      pull.close()
-    }
-    catch (err) {}
+    [pub, dealer, pull].forEach(function(sock) {
+      try {
+        sock.close()
+      }
+      catch (err) {
+        // No-op
+      }
+    })
   })
 }