Fix issue in ReplSuite with hadoop-provided profile.

When building the assembly with the maven "hadoop-provided"
profile, the executors were failing to come up because Hadoop classes
were not found in the classpath anymore; so add them explicitly to
the classpath using spark.executor.extraClassPath. This is only
needed for the local-cluster mode, but doesn't affect other tests,
so it's added for all of them to keep the code simpler.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #781 from vanzin/repl-test-fix and squashes the following commits:

4f0a3b0 [Marcelo Vanzin] Fix issue in ReplSuite with hadoop-provided profile.

repl/src/test/scala/org/apache/spark/repl/ReplSuite.scala

@@ -32,6 +32,8 @@ import org.apache.spark.util.Utils
 class ReplSuite extends FunSuite {
 
   def runInterpreter(master: String, input: String): String = {
+    val CONF_EXECUTOR_CLASSPATH = "spark.executor.extraClassPath"
+
     val in = new BufferedReader(new StringReader(input + "\n"))
     val out = new StringWriter()
     val cl = getClass.getClassLoader
@@ -44,13 +46,23 @@ class ReplSuite extends FunSuite {
         }
       }
     }
+    val classpath = paths.mkString(File.pathSeparator)
+
+    val oldExecutorClasspath = System.getProperty(CONF_EXECUTOR_CLASSPATH)
+    System.setProperty(CONF_EXECUTOR_CLASSPATH, classpath)
+
     val interp = new SparkILoop(in, new PrintWriter(out), master)
     org.apache.spark.repl.Main.interp = interp
-    interp.process(Array("-classpath", paths.mkString(File.pathSeparator)))
+    interp.process(Array("-classpath", classpath))
     org.apache.spark.repl.Main.interp = null
     if (interp.sparkContext != null) {
       interp.sparkContext.stop()
     }
+    if (oldExecutorClasspath != null) {
+      System.setProperty(CONF_EXECUTOR_CLASSPATH, oldExecutorClasspath)
+    } else {
+      System.clearProperty(CONF_EXECUTOR_CLASSPATH)
+    }
     return out.toString
   }