Fixed incorrect dropping of discovery request (https://issues.redhat.com/browse/JGRP-2840)

Author: belaban

src/org/jgroups/protocols/Discovery.java

@@ -360,9 +360,16 @@ else if(!cluster_name.equals(hdr.cluster_name)) {
                 }
                 if(max_rank_to_reply > 0 && hdr.initialDiscovery() && Util.getRank(view, local_addr) > max_rank_to_reply)
                     return null;
-                // Only send a response if hdr.mbrs is not empty and contains myself. Otherwise, always send my info
-                if (data != null && data.stream().map(PingData::mbrs).filter(Objects::nonNull).anyMatch(mbrs -> mbrs.contains(local_addr)))
-                    return null;
+                // Drop the response if PingData.mbrs is not empty/null and doesn't contain myself
+                // Otherwise, (mbrs==null) always send a response
+                if(data != null) {
+                    List<? extends Address> list=data.stream()
+                      .map(PingData::mbrs)
+                      .filter(Objects::nonNull)
+                      .flatMap(Collection::stream).collect(Collectors.toList());
+                    if(!list.isEmpty() && !list.contains(local_addr))
+                        return null;
+                }
                 PhysicalAddress physical_addr=(PhysicalAddress)down(new Event(Event.GET_PHYSICAL_ADDRESS, local_addr));
                 PingData p=new PingData(local_addr, is_server, NameCache.get(local_addr), physical_addr).coord(is_coord);
                 sendDiscoveryResponse(List.of(p), msg.src());