it should be connector="default"
as this is the name for default listener in undertow subsystem.
I figured out the problem. In the modcluster subsystem the connector connector="http" is the name of the http listener and in my case the name was default. So change the connector to connector="default" worked :-)
Thanks Tomaz Cerar I added this reply 2 min after you. I was typing the solution while you added the comment. :-)