When deploying my application (ear with a couple of jar and war files) on Wildfly 11.0.0.Beta1-SNAPSHOT I get warnings like this one for all the war files:
When deploying the same ear file on a Wildfly 10.1. this warning message does not appear.
Those war files raising the warnings do not contain RESTful Webservices, only SOAP based Webservices, and therefore do not need either servlet or class.
Only 2 sub modules contain RESTful Webservices and have a class extending javax.ws.rs.core.Application.
Following jaikiran's analysis, the existence of at least one JAX-RS subdeployment triggers the warning message for all other web modules in the war.