Description of problem:
2nd connection to Multi-Source Model Dynamic VDB is not Two-Phase Commit.

How reproducible:
Always

Steps to Reproduce:
Execute a update query via Multi-Source Model Dynamic VDB.
ex) 
vdb - maseter-vdb.xml
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>

<vdb name="MASTER-VDB" version="1">
  <description>A Dynamic VDB</description>
  <property name="UseConnectorMetadata" value="true" />
  <model visible="true" type="PHYSICAL" name="VDB1">
    <property name="supports-multi-source-bindings" value="true" />
    <source name="db02" translator-name="postgresql" connection-jndi-name="java:/PostgresXADS02" />
    <source name="db01" translator-name="postgresql" connection-jndi-name="java:/PostgresXADS01" />
  </model>
</vdb>
  
Additional info:
Set the multisourceUpdate flag as first query plan creating.

org.teiid.dqp.internal.process.multisource.MultiSourcePlanToProcessConverter.java
90:  @Override
91:  public synchronized RelationalPlan convert(PlanNode planNode)
92:      throws QueryPlannerException, TeiidComponentException {
93:      RelationalPlan result = null;
94:    try {
95:      result = super.convert(planNode);
96:      return result;
97:    } finally {
98:      if (result != null && update && multiSource) {
-> 99:        result.setMultisourceUpdate(true);
100:      }
101:      update = false;
102:      multiSource = false;
103:    }
104:  }

If multisourceUpdate is true, transactionService is started by teiid engine. But, second connects does not set the multisourceUpdate flag. Therefore, teiid engine does not start transactionService. 

org.teiid.dqp.internal.process.Request.java
338:  private void createProcessor() throws TeiidComponentException {
--- snip ---
349:    if(RequestMessage.TXN_WRAP_ON.equals(requestMsg.getTxnAutoWrapMode())){ 
350:      startAutoWrapTxn = true;
351:    } else if (RequestMessage.TXN_WRAP_DETECT.equals(requestMsg.getTxnAutoWrapMode())){
352:      boolean transactionalRead = requestMsg.getTransactionIsolation() == Connection.TRANSACTION_REPEATABLE_READ
353:        || requestMsg.getTransactionIsolation() == Connection.TRANSACTION_SERIALIZABLE;
-> 354:        startAutoWrapTxn = processPlan.requiresTransaction(transactionalRead);
355:    } 
356:
357:    if (startAutoWrapTxn) {
358:      try {
-> 359:        transactionService.begin(tc);
360:      } catch (XATransactionException err) {
361:        throw new TeiidComponentException(err);
362:      }
363:    }
364:  }

org.teiid.query.processor.relational.RelationalPlan.java
254:  @Override
255:  public boolean requiresTransaction(boolean transactionalReads) {
256:    if (multisourceUpdate) {
-> 257:      return true;
258:    }
259:    if (this.with != null) {
260:      if (transactionalReads) {
261:        return true;
262:      }
263:      for (WithQueryCommand withCommand : this.with) {
264:        if (withCommand.getCommand().getProcessorPlan().requiresTransaction(transactionalReads)) {
265:          return true;
266:        }
267:      }
268:    }
279:    return requiresTransaction(transactionalReads, root);
270:  }