[WFLY-2033] fix CMT NotSupported MDB

* fix handling tx attributes of MDB
* check that EJBContext.getUserTransaction() is allowed before calling
  the component
* add test org.jboss.as.test.integration.ejb.mdb.cmt.notsupported.ContainerManagedTransactionNotSupportedTestCase
WFLY-1409 custom mail server should allow definition of independent properties