Add schema for "urn:clustering:1.0" namespace to catalog

Schema for "urn:clustering:1.0" namespace is missing in catalog therefore JBDS complains when validating document with this namespace.

More details are in related Bugzilla with Customer Case: https://bugzilla.redhat.com/show_bug.cgi?id=1302544

PR fixing this issue in WildFly https://github.com/wildfly/wildfly/pull/6720 was rejected because it's deprecated schema for WildFly but since it's valid for EAP 6 it should be added to catalog.

EAP is not validating files against this schema it has custom validation for this namespace here https://github.com/jbossas/jboss-eap/blob/6.x/ejb3/src/main/java/org/jboss/as/ejb3/clustering/EJBBoundClusteringMetaDataParser.java#L57