Description of problem:
I see some warning logs during slave shutdown.

Version-Release number of selected component (if applicable):
EAP 6.3.0.ER8

How reproducible:
Always

Steps to Reproduce:
sed -i 's/<host/<host name=\"slave\"/g' ${EAP_HOME}/domain/configuration/host-slave.xml
# start master
./domain.sh --host-config=host-master.xml &
# start slave
./domain.sh --host-config=host-slave.xml -Djboss.domain.master.address=localhost -Djboss.management.native.port=12345 &
# stop the slave once the domain is fully booted
./jboss-cli.sh -c /host=slave:shutdown

Actual results:
[Host Controller] 12:57:46,477 INFO  [org.jboss.as.host.controller] (ProcessControllerConnection-thread - 2) JBAS010926: Unregistering server server-two
[Host Controller] 12:57:46,571 WARN  [org.jboss.msc.service.fail] (MSC service thread 1-4) MSC000004: Failure during stop of service jboss.host.controller.model.controller: java.util.concurrent.RejectedExecutionException: Task org.jboss.as.controller.AbstractControllerService$2@488eaf44 rejected from java.util.concurrent.ThreadPoolExecutor@f94be93[Terminated, pool size = 0, active threads = 0, queued tasks = 0, completed tasks = 10]
[Host Controller] 	at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2048) [rt.jar:1.7.0_45]
[Host Controller] 	at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:821) [rt.jar:1.7.0_45]
[Host Controller] 	at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1372) [rt.jar:1.7.0_45]
[Host Controller] 	at org.jboss.as.controller.AbstractControllerService.stop(AbstractControllerService.java:336) [jboss-as-controller-7.4.0.Final-redhat-17.jar:7.4.0.Final-redhat-17]
[Host Controller] 	at org.jboss.as.host.controller.DomainModelControllerService.stop(DomainModelControllerService.java:683) [jboss-as-host-controller-7.4.0.Final-redhat-17.jar:7.4.0.Final-redhat-17]
[Host Controller] 	at org.jboss.msc.service.ServiceControllerImpl$StopTask.stopService(ServiceControllerImpl.java:2088) [jboss-msc-1.1.5.Final-redhat-1.jar:1.1.5.Final-redhat-1]
[Host Controller] 	at org.jboss.msc.service.ServiceControllerImpl$StopTask.run(ServiceControllerImpl.java:2049) [jboss-msc-1.1.5.Final-redhat-1.jar:1.1.5.Final-redhat-1]
[Host Controller] 	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) [rt.jar:1.7.0_45]
[Host Controller] 	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) [rt.jar:1.7.0_45]
[Host Controller] 	at java.lang.Thread.run(Thread.java:744) [rt.jar:1.7.0_45]

Expected results:
No warning logs during slave shutdown.