BUG#11516 ndb_mgmd debug core on cluster shutdown with failed data nodes

Fix closing of sessions on mgm server shutdown.


ndb/include/mgmcommon/ConfigRetriever.hpp:
  Add disconnect();
ndb/src/common/mgmcommon/ConfigRetriever.cpp:
  Add disconnect() call so we can disconnect from the mgm server before it shuts down
  (if we are a mgm server).
ndb/src/mgmsrv/main.cpp:
  Close our ConfigRetriever connection first.
  
  Stop sessions, and wait for them to stop. (previously we didn't wait, this was
  causing core dumps on shutdown with failed nodes).

ndb/include/mgmcommon/ConfigRetriever.hpp

@@ -32,6 +32,7 @@ public:
   ~ConfigRetriever();
 
   int do_connect(int no_retries, int retry_delay_in_seconds, int verbose);
+  int disconnect();
   
   /**
    * Get configuration for current node.

ndb/src/common/mgmcommon/ConfigRetriever.cpp

@@ -107,6 +107,12 @@ ConfigRetriever::do_connect(int no_retries,
     0 : -1;
 }
 
+int
+ConfigRetriever::disconnect()
+{
+  return ndb_mgm_disconnect(m_handle);
+}
+
 //****************************************************************************
 //****************************************************************************
 //****************************************************************************

ndb/src/mgmsrv/main.cpp

@@ -353,7 +353,8 @@ int main(int argc, char** argv)
   
   g_eventLogger.info("Shutting down server...");
   glob.socketServer->stopServer();
-  glob.socketServer->stopSessions();
+  glob.mgmObject->get_config_retriever()->disconnect();
+  glob.socketServer->stopSessions(true);
   g_eventLogger.info("Shutdown complete");
   return 0;
  error_end: