Merge pull request apache#38 from derekd/make-thrift-purpose-static

Make Config.ThriftPurpose enum static.

Author: Bobby Evans

storm-core/src/jvm/backtype/storm/Config.java

@@ -244,7 +244,7 @@ public class Config extends HashMap<String, Object> {
     /**
      * The purpose for which the Thrift server is created.
      */
-    public enum ThriftServerPurpose {
+    public static enum ThriftServerPurpose {
         NIMBUS("nimbus.thrift"),
         DRPC("drpc.worker");