document transaction's state if an Exception occurs

It is not documented what happens with a transaction if a TImeoutException occurs while trying to acquire a lock.
E.g.
tm.begin()
caceh.put(k1); //this throws TE - what would be the status of the transaction after TE is thrown?
After discussing this on core, the suggestion was to make the transaction abort/rollback. This can be achieved by marking a tx as rollbackOnly.
Tests need to be added to enforce this behaviour and and documentation needs to be updated.