[1111064] Some code changes to avoid a locking issue. 

Presumably the issue has to so with passing an attached entity to an asynchronous slsb
method.  A few things:
- make sure we pass a deteched entity
- notify the alert condition-cache prior to calling the storage operation hook
- only call the storage operation hook for updates to existing history (not
  at operation schedule-time)
- remove an unnecessary outer Tx on runClusterMaintenance
- add some logging

Note: TODO: revert the hyped up scheduling of the cluster readrepair job