Minor Description
In NetworkTopology#pseudoSortByDistance, if no local node is found, it will always place the first rack local node in the list in front.
This became an issue when a dataset was loaded from a single datanode. This datanode ended up being the first replica for all the blocks in the dataset. When running an Impala query, the non-local reads when reading past a block boundary were all hitting this node, meaning massive load skew.
