We need to be able to override default protocol on a container level

Using <defaultProtocol type="Servlet 3.0" /> makes it impossible to run tests on tomcat-embedded-6.
We need to be able to override default protocol on a container level, so we can use defaultProtocol property and still share an arquillian.xml between older servers.

This is just a matter of honoring the protocol element child of the container element, which is already in the schema:

<container qualifier="jbossas-managed-7" default="true">
    <protocol type="Servlet 3.0"/>
</container>