Revert "Revert "Catch exception on server start""

This reverts commit 59f875e.

Author: martin-doyle

lib/server.js

@@ -216,6 +216,12 @@ function Server(opts, callback) {
         var server = interfaces.serverFactory(iface, fallback, that);
         that.servers.push(server);
         server.maxConnections = iface.maxConnections || 10000000;
+        
+        // Catch listen errors
+        server.on('error', function (e) {
+          that.logger.error('Error starting Mosca Server');
+          that.emit('error', e);
+        });        
         server.listen(port, host, dn);
       }, done);
     },