fixed #1464 - change so persistence dir is only backed up if node is HA ...

...master or HA disabled; handles the case of HA autodetect selecting master hence the complexity.

also fixes some leaks in test and improves atomic file update support in FileBasedObjectStore.
(incorporates new logging from #1469)
What is the use-case for `prepareForUse` being an explicit step for the caller? In the calls to it, they seem to instantiate + injectManagementContext + prepareForUse all in the same method. Is there some code external to core brooklyn that needs this?