Change default for keepalive autodisconnect config

By default, automatically disconnect if no response. This is preferable
because we can sometimes lose connectivity without receiving a close
event from the socket, but it's also possible that the endpoint may not
support responses.

// FREEBIE

libtextsecure/websocket-resources.js

@@ -165,7 +165,7 @@
             }
             this.disconnect = opts.disconnect;
             if (this.disconnect === undefined) {
-                this.disconnect = false;
+                this.disconnect = true;
             }
             this.wsr = websocketResource;
             this.reset();