This test simulates fact of disconnecting application server from network where both XA resources would need connection to its work.
TestXAResource behaves here by spec and we are checking how behaves the real XA resource.
Behaving by spec on connection failure means:
 - XAResource.prepare -> XAERR_RMFAIL
 - XAResource.commit -> XAERR_RMFAIL (or XA_RETRY)
 - XAResource.rollback -> XAERR_RMFAIL
     *
Test flow - JTA
1) prepare db/jms XA
2) stop connection to DB/JMS
3) prepare test XA
4) test XA simulates an error -> XAException.XAER_RMFAIL
5) doAbort phase
6) rollback db/jms XA (connection is down - jdbc driver throws
   XAException.XAER_RMFAIL for Oracle, DB2 and AMQ >EAP7.0.0.DR8; XAException.XAER_RMERR for others,
   specification says that XAER_RMERR means unexpected error and TM so behaves
   as the branch would be heuristic)
7) rollback test XA -> XAException.XAER_RMFAIL

JTS
===
JTS behaves differently from JTA as it consider TM manager being on a remote machine (not in the same JVM)
as the running code is. That has several implications - see https://developer.jboss.org/thread/260665
XAER_RMFAIL (client gets)
8) HeuristicException is returned to client, tm object log store contains uid in prepared state
recovery: leave the txn as it is as it has heuristic state and waiting for user so