Attempt to reparse topology files to recover from overlapping write

In gateway-server/src/main/java/org/apache/hadoop/gateway/topology/file/FileTopologyProvider.java
method loadTopology there needs to be a loop from the digester.parse onward. Within the loop there should be a try/catch for IOException and SAXException. If either of these are caught there should be a small sleep (e.g. 50ms) and then the parse should be reattempted. There should be a timeout for the whole loop such that it gives up within a short period (e.g. 250ms) and rethrows the last IOException or SAXException encountered.