[#257] pool/tree: Add node address to error

Signed-off-by: Denis Kirillov <d.kirillov@yadro.com>

pool/tree/pool.go

@@ -836,6 +836,11 @@ LOOP:
 				if startI != indexI || startJ != indexJ {
 					p.setStartIndices(indexI, indexJ)
 				}
+
+				if err != nil {
+					err = fmt.Errorf("address %s: %w", p.innerPools[indexI].clients[indexJ].endpoint(), err)
+				}
+
 				return err
 			}