ISPN-5023 Random Failues on *FactoryBeanTest in the Spring Modules

Force the test JMX domain even if the configuration was loaded from a file.

https://issues.jboss.org/browse/ISPN-5023

Oops, you're right, `SpringEmbeddedCacheManagerFactoryBeanTest` doesn't use `TestSpringEmbeddedCacheManagerFactoryBean` like `InfinispanEmbeddedCacheManagerFactoryBeanTest` uses `TestInfinispanEmbeddedCacheManagerFactoryBean`. No wonder Sebastian didn't see any reason to use the protected method :)