Improve tests in integration/multinode/../transaction/async/TransactionPropagationTestCase

This is for tests in testsuite/integration/multinode/src/test/java/org/jboss/as/test/multinode/transaction/async/TransactionPropagationTestCase.java

• replace the sleep() in test method with Future.get() after calling async methods
• improve jndi lookup
  • close context
  • cache context at class level
  • replace with @EJB injection