MXS-2196: Remove the dummy session

As each connection now immediately gets a session the dummy session is no
longer required. The next step would be to combine parts of the session
and the client DCB into one entity. This would prevent the possibility of
a client DCB with no associated session. Backend DCBs are different as
they can move from one session to another when the persistent connection
pool is in use.

server/modules/protocol/CDC/cdc.cc

@@ -293,9 +293,6 @@ static int cdc_accept(DCB* client_dcb)
 
     client_dcb->protocol = (CDC_protocol*) protocol;
 
-    /* Dummy session */
-    client_dcb->session = session_set_dummy(client_dcb);
-
     if (NULL == client_dcb->session || poll_add_dcb(client_dcb))
     {
         dcb_close(client_dcb);