ISPN-4112 RHQ library plugin: restart cache -- availability report DOWN

but cache running

* Added back in availibilty down for cache not running
* Added server changes to also report DOWN when cache not running

https://issues.jboss.org/browse/ISPN-4112
Sure I can toy with the refreshAttributes(List<String>) method.  It looks like it should be more performant.

https://github.com/rhq-project/ems/blob/master/src/ems-impl/org/mc4j/ems/impl/jmx/connection/bean/DMBean.java#L248