Use synchronizations as a default transactional mode rather than XA

Transactions are being enlisted as XAResources with recovery disabled by default.

XAResource enlistment without recovery does not bring any benefit over Synchronization enlistment, which is more efficient(30-40%). See http://infinispan.blogspot.com/2011/06/transactions-enhancements-in-50.html

So the suggested enlistment should be Synchronization (default). Also if xa-enlistment is preferred then recovery should be enabled by default - there's little reason in using XAResource enlistment without recovery.