mDNS browser does not discover registries after a reset

[Mammouth2727]

In NodeAPI.js, the resetMDNS function tries to stop the service browser (browser.stop()) and then invokes browser.discover() to make it discover services again. By looking at the mdns-js browser code we can see that this can't work since the stop method unregisters the browser instance from its own networking sub-layer. To fix this, two options : add a 'start' function in mdns-js Browser or simply recreate a new browser instance in resetMDNS.

This can be easily simulated by running the BBC IPStudio VM, stopping and starting the registry
sudo service ips-regaggregator stop
sudo service ips-regaggregator start