[GSS](7.3.z) Document Multiple Cluster Use Case with EJB

The example configurations, the 'cluster' name defaults to 'ejb'.
By default an ejb client will have cluster affinity to the cluster in which the node if first invokes belongs.
When an environment has more than 1 cluster and an ejb client that talks to more than 1 cluster, the clustered server configurations must set a unique 'cluster' name.

        <subsystem xmlns="urn:jboss:domain:jgroups:7.0">
            <channels default="ee">
                <channel name="ee" stack="udp" cluster="ejb"/>
            </channels>

An ejb client needing to invoke EJBs on the different clusters would:

• use the providerURL to point to a node in the cluster it wants to invoke
• or specify a strong cluster affinity to the cluster it wants to invoke