Return delete success for pods that never got scheduled

(cherry picked from commit b0b2fc1)

ipamd/rpc_handler.go

@@ -93,7 +93,14 @@ func (s *server) DelNetwork(ctx context.Context, in *pb.DelNetworkRequest) (*pb.
 	}
 	log.Infof("Send DelNetworkReply: IPv4Addr %s, DeviceNumber: %d, err: %v", ip, deviceNumber, err)
 
-	return &pb.DelNetworkReply{Success: err == nil, IPv4Addr: ip, DeviceNumber: int32(deviceNumber)}, nil
+	// Plugins should generally complete a DEL action without error even if some resources are missing. For example,
+	// an IPAM plugin should generally release an IP allocation and return success even if the container network
+	// namespace no longer exists, unless that network namespace is critical for IPAM management
+	success := true
+	if err != nil && err != datastore.ErrUnknownPod {
+		success = false
+	}
+	return &pb.DelNetworkReply{Success: success, IPv4Addr: ip, DeviceNumber: int32(deviceNumber)}, nil
 }
 
 // RunRPCHandler handles request from gRPC