change error for retriable error in getting last modification change

SVN: 26634

common/source/java/ch/systemsx/cisd/common/filesystem/RemoteDirectoryCopyActivitySensor.java

@@ -61,7 +61,8 @@ public final class RemoteDirectoryCopyActivitySensor extends AbstractCopyActivit
             return StatusWithResult.create(lastChanged);
         } catch (UnknownLastChangedException ex)
         {
-            return StatusWithResult.<Long> createError("Cannot determine time of last change of "
+            return StatusWithResult
+                    .<Long> createRetriableError("Cannot determine time of last change of "
                     + getTargetDescription());
         }
     }