Add more tests for the JTS implementation of ExtendedJBossXATerminator

ExtendedJBossXATerminator is our (extended) SPI interface for importing transactions and it has both JTA and JTS implementations. It is used by EJB in JTA mode which will be fully exercising the interface in JTA mode. However, we only test a subset of the interface in JTS mode (see com.arjuna.ats.jta.distributed.SimpleIsolatedServers) and these need extending to cover all of the methods.

Note that at least one of the methods is known not to produce the correct result, namely

public Transaction getTransaction(Xid xid) throws XAException

because the implementation uses XATxConverter to lookup the transaction but XATxConverter uses a different Xid format id from the one used by JTS so it will return null (instead of the transaction corresponding to the input xid).