According to the javadoc for XATerminator, it should include an error code in the XAException thrown:
e.g. see
http://java.sun.com/j2ee/1.4/docs/api/javax/resource/spi/XATerminator.html#prepare(javax.transaction.xa.Xid)

This is similar to the fix for the JBossXALocalException done in JBAS-2807

However, our XATerminator impl in TxManager is not including the error code in the thrown XAException.

I'm attaching a diff that shows how to fix this for prepare(), i.e. add XA_RBROLLBACK
but this also needs doing for the other methods commit/forget/rollback
and tests creating to prevent regression.