Reduce contention points in Commit Queue
Reduce contention in CommitLog
Reduce getConfiguration timeout when a node joins
Return immediately if no transactions are ready to commit
Increase log level when an exception is thrown during the CommitCommand
Add JMX info about enqueue transactions
Consistency fix: new validation scheme

* The validation did not take in account the non-visible versions set.
This can lead a transaction to be committed while it should be aborted,
creating inconsistencies in the data
Skip send the 3rd phase command for GMU
Fix compilation error