Parallel nested transactions had a bug on the abort procedure.

A test was added that explains the problem along with the fix on the corresponding file.
In summary, more than one depth of nesting could cause a top level transaction to incorrectly take ownership of a VBox from another top level transaction.
Bug fix on abort of a parallel nested transaction with depth > 2
Merge pull request #13 from smmf/smf-fix-direct-commits-on-master

fix direct commits on master