Fix testing with Python3 (#424)

Fix print statement in tests to be Python 2 and Python 3 compatible. #408
diff --git a/server/src/test/scala/org/apache/livy/server/batch/BatchServletSpec.scala b/server/src/test/scala/org/apache/livy/server/batch/BatchServletSpec.scala
index 5a84035..de74ebe 100644
--- a/server/src/test/scala/org/apache/livy/server/batch/BatchServletSpec.scala
+++ b/server/src/test/scala/org/apache/livy/server/batch/BatchServletSpec.scala
@@ -43,7 +43,7 @@
     try {
       writer.write(
         """
-          |print "hello world"
+          |print("hello world")
         """.stripMargin)
     } finally {
       writer.close()
diff --git a/server/src/test/scala/org/apache/livy/server/batch/BatchSessionSpec.scala b/server/src/test/scala/org/apache/livy/server/batch/BatchSessionSpec.scala
index 20e6136..401a8be 100644
--- a/server/src/test/scala/org/apache/livy/server/batch/BatchSessionSpec.scala
+++ b/server/src/test/scala/org/apache/livy/server/batch/BatchSessionSpec.scala
@@ -48,7 +48,7 @@
     try {
       writer.write(
         """
-          |print "hello world"
+          |print("hello world")
         """.stripMargin)
     } finally {
       writer.close()