Using multiple DefaultCacheManager w/o jmx leads to JmxDomainConflictException

Creating multiple instances of DefaultCacheManager leads to CacheManagerJmxRegistrationTest, even when JMX is disabled in configuration.

org.infinispan.jmx.JmxDomainConflictException: Domain already registered org.infinispan when trying to register: type=CacheManager,name="DefaultCacheManager"
at org.infinispan.jmx.JmxUtil.buildJmxDomain(JmxUtil.java:75)
at org.infinispan.jmx.CacheManagerJmxRegistration.updateDomain(CacheManagerJmxRegistration.java:101)
at org.infinispan.jmx.CacheManagerJmxRegistration.buildRegistrar(CacheManagerJmxRegistration.java:95)
at org.infinispan.jmx.AbstractJmxRegistration.registerMBeans(AbstractJmxRegistration.java:59)
at org.infinispan.jmx.CacheManagerJmxRegistration.start(CacheManagerJmxRegistration.java:63)
at org.infinispan.manager.DefaultCacheManager.start(DefaultCacheManager.java:705)
at org.infinispan.manager.DefaultCacheManager.<init>(DefaultCacheManager.java:300)
at org.infinispan.manager.DefaultCacheManager.<init>(DefaultCacheManager.java:171)

Update

This also happens when using CDI Extension in Library mode with Wildfly. Attached Pull Request fixes that case.