ISPN-4644 & ISPN-4258 MassIndexer performance enhancements

https://issues.jboss.org/browse/ISPN-4644
https://issues.jboss.org/browse/ISPN-4258

Instead of committing on each individual document plus on each map execution, it will commit only once per MassIndexer execution.
Also avoid using the SharedWorkspace setting on all MassIndexer tests, since it does heavy synchronization assuming the index is shared (which is not)