Fixes compilation error in HadoopDruidIndexerNode.java

...arStream.

[ERROR] /Users/bone/git/boneill42/druid/indexer/src/main/java/com/metamx/druid/indexer/HadoopDruidIndexerNode.java:[100,39] cannot find symbol
[ERROR] symbol  : method toString(<anonymous com.google.common.io.InputSupplier<java.lang.Readable>>)