Skip trying to send system events just before shutdown

Signed-off-by: Waldemar Quevedo <wally@nats.io>

server/events.go

@@ -633,6 +633,11 @@ func (s *Server) sendInternalAccountMsgWithReply(a *Account, subject, reply stri
 	s.mu.RLock()
 	if s.sys == nil || s.sys.sendq == nil {
 		s.mu.RUnlock()
+               if s.isShuttingDown() {
+                       // Skip in case this was called at the end phase during shut down
+                       // to avoid too many entries in the logs.
+                       return nil
+               }
 		return ErrNoSysAccount
 	}
 	c := s.sys.client