Description of problem:

Adding the modcluster subsystem and then reloading hits an IllegalStateException upon reload:

java.lang.IllegalStateException: JBAS018786: Multiple Deployment Unit registered processors with priority class 7170 and class org.jboss.as.modcluster.ModClusterServiceWebDependencyProcessor
at org.jboss.as.server.DeployerChainAddHandler.addDeploymentProcessor(DeployerChainAddHandler.java:63)
	at org.jboss.as.server.AbstractDeploymentChainStep$1.addDeploymentProcessor(AbstractDeploymentChainStep.java:40)
	at org.jboss.as.modcluster.ModClusterSubsystemAdd$1.execute(ModClusterSubsystemAdd.java:96)
	at org.jboss.as.server.AbstractDeploymentChainStep.execute(AbstractDeploymentChainStep.java:50)
	at org.jboss.as.controller.AbstractOperationContext.executeStep(AbstractOperationContext.java:702) [jboss-as-controller-7.5.0.Final-redhat-21.jar:7.5.0.Final-redhat-21]
	at org.jboss.as.controller.AbstractOperationContext.doCompleteStep(AbstractOperationContext.java:537) [jboss-as-controller-7.5.0.Final-redhat-21.jar:7.5.0.Final-redhat-21]
	at org.jboss.as.controller.AbstractOperationContext.completeStepInternal(AbstractOperationContext.java:338)


Version-Release number of selected component (if applicable):

EAP 6.4.4

How reproducible:

Always

Steps to Reproduce:
1. Start JBoss with default standalone.xml
2. Issue following CLI commands

[standalone@localhost:9999 /] /extension=org.jboss.as.modcluster:add
[standalone@localhost:9999 /] batch
[standalone@localhost:9999 / #] /subsystem=modcluster:add()
[standalone@localhost:9999 / #] /subsystem=modcluster/mod-cluster-config=configuration:add(connector=http,advertise="false",proxy-list="127.0.0.1:6666")
[standalone@localhost:9999 / #] run-batch
[standalone@localhost:9999 /] :reload


3. Note the error upon reload

Actual results:

JBoss fails upon reload after adding the modcluster subsystem


Expected results:

JBoss does not fail upon reload after adding the modcluster subsystem


Additional info:

EAP 6 currently adds modcluster through a runtime operation so the commands leave a ModClusterServiceWebDependencyProcessor in the DeployerChainAddHandler deployerMap, allowing for the reload failure.  Upstream wildfly modcluster uses a boottime operation, which avoids this issue, so EAP 6 should likely do the same.