Deployment fails when jboss-web.xml contains <enable-websockets>true</enable-websockets>

When deploying application with WebSockets used in EAP 6 to EAP 7, deployment will fail due EAP7 not supporting [1] in jboss-web.xml. The <enable-websockets> element is required in EAP 6 to enable the WebSockets functionality in JBoss Web.

This element should be also allowed in EAP 7 in order to simplify migration from EAP 6. Functionality of {{ <enable-websockets>true</enable-websockets>}} can be ignored as in EAP 7 and in Undertow there is no need to enable WebSockets explicitly.

[1]

<jboss-web version="7.2"
   xmlns="http://www.jboss.com/xml/ns/javaee"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://www.jboss.com/xml/ns/javaee schema/jboss-web_7_2.xsd">
    <enable-websockets>true</enable-websockets>
</jboss-web>