WildFly Test Suite: Integration - XTS is a little bit confusing and needs small cleanup

The line https://github.com/wildfly/wildfly/blob/master/testsuite/integration/xts/src/test/java/org/jboss/as/test/xts/wsba/coordinatorcompletion/client/BACoordinatorCompletionTestCase.java#L124 is never reached because exception is thrown from the line before.

The Javadoc https://github.com/wildfly/wildfly/blob/master/testsuite/integration/xts/src/test/java/org/jboss/as/test/xts/wsba/coordinatorcompletion/service/BACoordinationCompletionParticipant.java is copied from https://github.com/wildfly/quickstart/blob/10.x/wsba-coordinator-completion-simple/src/main/java/org/jboss/as/quickstarts/wsba/coordinatorcompletion/simple/SetParticipantBA.java and doesn't make sense here.