MODE-2216 Fixed the potential corruption of the workspace cache during concurrent modification of the same nodes.

With the previous code, multiple session writers of the same nodes could cause a "transient" (local) change to be loaded in the workspace cache during the `persistChanges` call. This because changed nodes are cleared asynchronously from the workspace cache which is not subject to ISPN locking.

The solution was to use a "transient" workspace cache during the `persistChanges` call, which always contains the latest ISPN stored data after locks have been successfully obtained.