Bug 1128614 - RHQ 4.12 high CPU usage in hibernate thread (java.util.regex.Pattern$Start.match)

EAP up to 6.3 included has an issue with the JIPI implementation which cause high CPU usage when reading the Hibernate Persistence Unit with :read-resource.

High CPU usage was detected when checking for availability and loading configuration. So the fix consists in:

* BaseComponent#getAvailability change
Read only minimum information as we just want to make sure we can read the resource. There's no need to read the children names, evaluate defaults, and retrieve runtime attributes.

* HibernatePersistenceUnitComponent#loadConfiguration addition
Reading the "enabled" attribute is the only thing needed.

These changes not only fix the issue but generally improve performance in the AS7 plugin (less data sent over the AS7 management connection).

(cherry picked from commit b5e8b3b09d5f05506ecd723feeeb1be5be1af6e5)