[SPARK-7233] [CORE] Detect REPL mode once

<h3>Description</h3>
Detect REPL mode once per JVM lifespan.
Previous behavior was to check presence of interpreter mode every time a job was submitted. In the case of execution of multiple short-living jobs this was causing massive mutual blocks between submission threads.

For more details please refer to https://issues.apache.org/jira/browse/SPARK-7233.

<h3>Notes</h3>
* I inverted the return value in case of catching an exception from `true` to `false`. It seems more logical to assume that if the REPL class is not found, we aren't in the interpreter mode.
* I'd personally would call `classForName` with just a Spark classloader (`org.apache.spark.util.Utils#getSparkClassLoader`) but `org.apache.spark.util.Utils#getContextOrSparkClassLoader` is said to be preferable.
* I struggled to come up with a concise, readable and clear unit test. Suggestions are welcome if you feel necessary.

Author: Oleksii Kostyliev <etander@gmail.com>
Author: Oleksii Kostyliev <okostyliev@thunderhead.com>

Closes #5835 from preeze/SPARK-7233 and squashes the following commits:

69bb9e4 [Oleksii Kostyliev] SPARK-7527: fixed explanatory comment to meet style-checker requirements
26dcc24 [Oleksii Kostyliev] SPARK-7527: fixed explanatory comment to meet style-checker requirements
c6f9685 [Oleksii Kostyliev] Merge remote-tracking branch 'remotes/upstream/master' into SPARK-7233
b78a983 [Oleksii Kostyliev] SPARK-7527: revert the fix and let it be addressed separately at a later stage
b64d441 [Oleksii Kostyliev] SPARK-7233: inline inInterpreter parameter into instantiateClass
86e2606 [Oleksii Kostyliev] SPARK-7233, SPARK-7527: Handle interpreter mode properly.
c7ee69c [Oleksii Kostyliev] Merge remote-tracking branch 'upstream/master' into SPARK-7233
d6c07fc [Oleksii Kostyliev] SPARK-7233: properly handle the inverted meaning of isInInterpreter
c319039 [Oleksii Kostyliev] SPARK-7233: move inInterpreter to Utils and make it lazy

core/src/main/scala/org/apache/spark/util/ClosureCleaner.scala

@@ -239,15 +239,6 @@ private[spark] object ClosureCleaner extends Logging {
     logDebug(s" + fields accessed by starting closure: " + accessedFields.size)
     accessedFields.foreach { f => logDebug("     " + f) }
 
-    val inInterpreter = {
-      try {
-        val interpClass = Class.forName("spark.repl.Main")
-        interpClass.getMethod("interp").invoke(null) != null
-      } catch {
-        case _: ClassNotFoundException => true
-      }
-    }
-
     // List of outer (class, object) pairs, ordered from outermost to innermost
     // Note that all outer objects but the outermost one (first one in this list) must be closures
     var outerPairs: List[(Class[_], AnyRef)] = (outerClasses zip outerObjects).reverse
@@ -274,7 +265,7 @@ private[spark] object ClosureCleaner extends Logging {
       // required fields from the original object. We need the parent here because the Java
       // language specification requires the first constructor parameter of any closure to be
       // its enclosing object.
-      val clone = instantiateClass(cls, parent, inInterpreter)
+      val clone = instantiateClass(cls, parent)
       for (fieldName <- accessedFields(cls)) {
         val field = cls.getDeclaredField(fieldName)
         field.setAccessible(true)
@@ -327,9 +318,8 @@ private[spark] object ClosureCleaner extends Logging {
 
   private def instantiateClass(
       cls: Class[_],
-      enclosingObject: AnyRef,
-      inInterpreter: Boolean): AnyRef = {
-    if (!inInterpreter) {
+      enclosingObject: AnyRef): AnyRef = {
+    if (!Utils.isInInterpreter) {
       // This is a bona fide closure class, whose constructor has no effects
       // other than to set its fields, so use its constructor
       val cons = cls.getConstructors()(0)

core/src/main/scala/org/apache/spark/util/Utils.scala

@@ -1795,6 +1795,20 @@ private[spark] object Utils extends Logging {
     }
   }
 
+  lazy val isInInterpreter: Boolean = {
+    try {
+      val interpClass = classForName("spark.repl.Main")
+      interpClass.getMethod("interp").invoke(null) != null
+    } catch {
+      // Returning true seems to be a mistake.
+      // Currently changing it to false causes tests failures in Streaming.
+      // For a more detailed discussion, please, refer to
+      // https://github.com/apache/spark/pull/5835#issuecomment-101042271 and subsequent comments.
+      // Addressing this changed is tracked as https://issues.apache.org/jira/browse/SPARK-7527
+      case _: ClassNotFoundException => true
+    }
+  }
+
   /**
    * Return a well-formed URI for the file described by a user input string.
    *