#83 Bug with setRollbackOnly for MDB fixed.

[Peter Antman]

setRollbackOnly for MDB did not work correct.

Reason: the value it checked in MessageDrivenMetadata
was not set during deployment since it relied on
ApplicationMedatadata, before that class has fully done
its jobb. That is, it tried to lookup the
methodTransaction atribute befor it was set.

The logic has now changed and MessageDrivenMetadata
overrides the getMethodTransactionType and cached the
result. MessageDrivenEnterpriseContext also now instead
relies on getMethodTransactionType() instead.