Remove invalid test in XmppStateMachineTest

In the test Established_EvTcpClose_Then_EvXmppMessageStreamHeader,
EvXmppMessageStreamHeader is injected into a session_ XmppSession *, after
injecting EvTcpClose event. This is an invalid scenario because as a result of
processing EvTcpClose, XmppSession *session pointer can/will get destroyed.
Hence, we should not enqueue EvXmppMessageStreamHeader over a deleted session
later on. This can cause the test to crash and hence makes this test case in
xmpp_server_sm_test flaky.

Change-Id: I66b257c49ede25e4142d93aa0264f729b1896031
Closes-Bug: 1758806

src/xmpp/test/xmpp_server_sm_test.cc

@@ -383,30 +383,6 @@ TEST_F(XmppStateMachineTest, Established_EvTcpClose) {
     VerifyState(xmsm::IDLE);
 }
 
-// Old State : Established
-// Event     : EvTcpClose + EvXmppMessageStreamHeader
-// New State : Idle
-// Intent    : EvXmppMessageStreamHeader should not be processed when the
-//             session is no longer associated with the connection due to
-//             processing of EvTcpClose
-TEST_F(XmppStateMachineTest,
-       Established_EvTcpClose_Then_EvXmppMessageStreamHeader) {
-    VerifyState(xmsm::ACTIVE);
-
-    EvTcpPassiveOpenFake();
-    VerifyState(xmsm::ACTIVE);
-
-    EvXmppOpen();
-
-    VerifyState(xmsm::ESTABLISHED);
-
-    EvTcpClose();
-    VerifyState(xmsm::IDLE);
-
-    EvXmppMessageStreamHeader();
-    VerifyState(xmsm::IDLE);
-}
-
 // Old State : Established
 // Event     : EvStop
 // New State : Idle