[SPARK-15633][minor] Make package name for Java tests consistent

[rxin]

What changes were proposed in this pull request?

This is a simple patch that makes package names for Java 8 test suites consistent. I moved everything to test.org.apache.spark to we can test package private APIs properly. Also added "java8" as the package name so we can easily run all the tests related to Java 8.

How was this patch tested?

This is a test only change.

[rxin]

cc @andrewor14

[srowen]

Yeah, core tests use test.org.apache.spark to specifically test from outside the same package. Is .java8 needed? I don't particularly care much myself. Some scala tests use org.apache.sparktest, unfortunately.

[rxin]

the java8 part is to make it easier to run all java 8 tests. not that big of a deal though. the more important one is to make the beginning part consistent.

[SparkQA]

Test build #59527 has finished for PR 13364 at commit f44883f.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • public class Java8RDDAPISuite implements Serializable
  • public class Java8APISuite extends LocalJavaStreamingContext implements Serializable
  • public class Java8DatasetAggregatorSuite extends JavaDatasetAggregatorSuiteBase
  • class JDK8ScalaSuite extends SparkFunSuite with SharedSparkContext
  • public class JavaDatasetAggregatorSuite extends JavaDatasetAggregatorSuiteBase
  • static class IntSumOf extends Aggregator<Tuple2<String, Integer>, Integer, Integer>
  • public class JavaDatasetAggregatorSuiteBase implements Serializable
  • public class JavaSaveLoadSuite

[SparkQA]

Test build #3029 has finished for PR 13364 at commit f44883f.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • public class Java8RDDAPISuite implements Serializable
  • public class Java8APISuite extends LocalJavaStreamingContext implements Serializable
  • public class Java8DatasetAggregatorSuite extends JavaDatasetAggregatorSuiteBase
  • class JDK8ScalaSuite extends SparkFunSuite with SharedSparkContext
  • public class JavaDatasetAggregatorSuite extends JavaDatasetAggregatorSuiteBase
  • static class IntSumOf extends Aggregator<Tuple2<String, Integer>, Integer, Integer>
  • public class JavaDatasetAggregatorSuiteBase implements Serializable
  • public class JavaSaveLoadSuite

[rxin]

Merging in master/2.0.