Fix broken Json tests.

The assertJsonStringEquals method was missing an "assert" so
did not actually check that the strings were equal. This commit
adds the missing assert and fixes subsequently revealed problems
with the JsonProtocolSuite.

@andrewor14 I changed some of the test functionality to match what it
looks like you intended based on the expected strings -- let me know if
anything here looks wrong.

Author: Kay Ousterhout <kayousterhout@gmail.com>

Closes #1198 from kayousterhout/json_test_fix and squashes the following commits:

77f858f [Kay Ousterhout] Fix broken Json tests.

core/src/test/scala/org/apache/spark/util/JsonProtocolSuite.scala

@@ -366,7 +366,7 @@ class JsonProtocolSuite extends FunSuite {
 
   private def assertJsonStringEquals(json1: String, json2: String) {
     val formatJsonString = (json: String) => json.replaceAll("[\\s|]", "")
-    formatJsonString(json1) === formatJsonString(json2)
+    assert(formatJsonString(json1) === formatJsonString(json2))
   }
 
   private def assertSeqEquals[T](seq1: Seq[T], seq2: Seq[T], assertEquals: (T, T) => Unit) {
@@ -449,7 +449,7 @@ class JsonProtocolSuite extends FunSuite {
   }
 
   private def makeStageInfo(a: Int, b: Int, c: Int, d: Long, e: Long) = {
-    val rddInfos = (1 to a % 5).map { i => makeRddInfo(a % i, b % i, c % i, d % i, e % i) }
+    val rddInfos = (0 until a % 5).map { i => makeRddInfo(a + i, b + i, c + i, d + i, e + i) }
     new StageInfo(a, "greetings", b, rddInfos, "details")
   }
 
@@ -493,20 +493,19 @@ class JsonProtocolSuite extends FunSuite {
   private val stageSubmittedJsonString =
     """
       {"Event":"SparkListenerStageSubmitted","Stage Info":{"Stage ID":100,"Stage Name":
-      "greetings","Number of Tasks":200,"RDD Info":{"RDD ID":100,"Name":"mayor","Storage
-      Level":{"Use Disk":true,"Use Memory":true,"Use Tachyon":false,"Deserialized":true,
-      "Replication":1},"Number of Partitions":200,"Number of Cached Partitions":300,
-      "Memory Size":400,"Disk Size":500,"Tachyon Size":0},"Emitted Task Size Warning":false},
-      "Properties":{"France":"Paris","Germany":"Berlin","Russia":"Moscow","Ukraine":"Kiev"}}
+      "greetings","Number of Tasks":200,"RDD Info":[],"Details":"details",
+      "Emitted Task Size Warning":false},"Properties":{"France":"Paris","Germany":"Berlin",
+      "Russia":"Moscow","Ukraine":"Kiev"}}
     """
 
   private val stageCompletedJsonString =
     """
       {"Event":"SparkListenerStageCompleted","Stage Info":{"Stage ID":101,"Stage Name":
-      "greetings","Number of Tasks":201,"RDD Info":{"RDD ID":101,"Name":"mayor","Storage
+      "greetings","Number of Tasks":201,"RDD Info":[{"RDD ID":101,"Name":"mayor","Storage
       Level":{"Use Disk":true,"Use Memory":true,"Use Tachyon":false,"Deserialized":true,
       "Replication":1},"Number of Partitions":201,"Number of Cached Partitions":301,
-      "Memory Size":401,"Disk Size":501,"Tachyon Size":0},"Emitted Task Size Warning":false}}
+      "Memory Size":401,"Tachyon Size":0,"Disk Size":501}],"Details":"details",
+      "Emitted Task Size Warning":false}}
     """
 
   private val taskStartJsonString =
@@ -538,9 +537,9 @@ class JsonProtocolSuite extends FunSuite {
       900,"Total Blocks Fetched":1500,"Remote Blocks Fetched":800,"Local Blocks Fetched":
       700,"Fetch Wait Time":900,"Remote Bytes Read":1000},"Shuffle Write Metrics":
       {"Shuffle Bytes Written":1200,"Shuffle Write Time":1500},"Updated Blocks":
-      [{"Block ID":{"Type":"RDDBlockId","RDD ID":0,"Split Index":0},"Status":
-      {"Storage Level":{"Use Disk":true,"Use Memory":true,"Use Tachyon":false,
-      "Deserialized":false,"Replication":2},"Memory Size":0,"Disk Size":0,"Tachyon Size":0}}]}}
+      [{"Block ID":"rdd_0_0","Status":{"Storage Level":{"Use Disk":true,"Use Memory":true,
+      "Use Tachyon":false,"Deserialized":false,"Replication":2},"Memory Size":0,"Tachyon Size":0,
+      "Disk Size":0}}]}}
     """
 
   private val jobStartJsonString =