Update node affinity to K8s 1.6 spec (#12)

I'm proposing and edit to this file that is inline with the K8s 1.6 affinity spec.

Author: eddieesquivel

charts/hdfs-datanode-k8s/templates/datanode-daemonset.yaml

@@ -24,28 +24,6 @@ spec:
     metadata:
       labels:
         name: hdfs-datanode
-      annotations:
-        # TODO: The following uses annotation to express affinity
-        # because Kubernetes 1.5 supports affinity only in annotation as alpha
-        # feature. In Kubernetes 1.6, this is now beta and supports regular
-        # YAML construct. Switch to the official syntax when we support 1.6.
-        scheduler.alpha.kubernetes.io/affinity: >
-          {
-            "nodeAffinity": {
-              "requiredDuringSchedulingIgnoredDuringExecution": {
-                "nodeSelectorTerms": [
-                  {
-                    "matchExpressions": [
-                      {
-                        "key": "hdfs-datanode-exclude",
-                        "operator": "DoesNotExist"
-                      }
-                    ]
-                  }
-                ]
-              }
-            }
-          }
     spec:
       hostNetwork: true
       hostPID: true
@@ -89,6 +67,13 @@ spec:
             - name: resolv-conf-volume
               mountPath: /etc/resolv.conf
               subPath: resolv.conf
+      affinity:
+        nodeAffinity:
+          requiredDuringSchedulingIgnoredDuringExecution:
+            nodeSelectorTerms:
+              - matchExpressions:
+                - key: hdfs-datanode-exclude
+                  operator: DoesNotExist
       restartPolicy: Always
       volumes:
         {{- range $index, $path := .Values.dataNodeHostPath }}