Stop hiding inbox instead of closing

This behavior was intended to help keep the websocket alive, but keeping
the inbox window around can cause some stale frontend state. Also we now
have a keepalive alarm to check for new messages once a minute.

js/views/window_controls_view.js

@@ -30,11 +30,7 @@
             'click .minimize': 'minimize'
         },
         close: function() {
-            if (this.appWindow.id === 'inbox') {
-                this.appWindow.hide();
-            } else {
-                this.appWindow.close();
-            }
+            this.appWindow.close();
         },
         minimize: function() {
           this.appWindow.minimize();