Merge pull request alteryx#27 from davidmccauley/master

SPARK-920/921 - JSON endpoint updates

920 - Removal of duplicate scheme part of Spark URI, it was appearing as spark://spark//host:port in the JSON field.

JSON now delivered as:
url:spark://127.0.0.1:7077

921 - Adding the URL of the Main Application UI will allow custom interfaces (that use the JSON output) to redirect from the standalone UI.

(cherry picked from commit 100222b)
Signed-off-by: Reynold Xin <rxin@apache.org>

core/src/main/scala/org/apache/spark/deploy/JsonProtocol.scala

@@ -41,6 +41,7 @@ private[spark] object JsonProtocol {
     ("starttime" -> obj.startTime) ~
     ("id" -> obj.id) ~
     ("name" -> obj.desc.name) ~
+    ("appuiurl" -> obj.appUiUrl) ~
     ("cores" -> obj.desc.maxCores) ~
     ("user" ->  obj.desc.user) ~
     ("memoryperslave" -> obj.desc.memoryPerSlave) ~
@@ -64,7 +65,7 @@ private[spark] object JsonProtocol {
   }
 
   def writeMasterState(obj: MasterStateResponse) = {
-    ("url" -> ("spark://" + obj.uri)) ~
+    ("url" -> obj.uri) ~
     ("workers" -> obj.workers.toList.map(writeWorkerInfo)) ~
     ("cores" -> obj.workers.map(_.cores).sum) ~
     ("coresused" -> obj.workers.map(_.coresUsed).sum) ~