Improve startup time by ensuring that the Object Store MBean does not probe the logs in its start method

There is an MBean called com.arjuna.ats.arjuna.tools.osb.mbean.ObjStoreBrowser that we use to expose transaction logs to the tooling. The start method probes (by calling the probe() method) the object store and creates MBeans for each log record it finds. We can improve boot time performance if the probe call is removed (it happens on demand anyway so will have zero impact on functionality).