Better handling of online/offline behavior, socket shutdown (#1593)

* Online/offline: Always stop timer, don't connect if closed

* Sockets: Send our own close event faster, shutdown only on close

Seems that we were too-aggressively disconnecting from all socket
events. Also, we should be able to send our own close event a lot
faster with no ill effects.

* Catch-up libtextsecure changes

libtextsecure/message_receiver.js

@@ -28,6 +28,10 @@ MessageReceiver.prototype = new textsecure.EventTarget();
 MessageReceiver.prototype.extend({
     constructor: MessageReceiver,
     connect: function() {
+        if (this.calledClose) {
+            return;
+        }
+
         this.hasConnected = true;
 
         if (this.socket && this.socket.readyState !== WebSocket.CLOSED) {
@@ -78,8 +82,6 @@ MessageReceiver.prototype.extend({
             this.wsr.close(3000, 'called close');
         }
 
-        this.shutdown();
-
         return this.drain();
     },
     onopen: function() {