[SPARK-6765] Enable scalastyle on test code.

[rxin]

Turn scalastyle on for all test code. Most of the violations have been resolved in my previous pull requests:

Core: #5484
SQL: #5412
MLlib: #5411
GraphX: #5410
Streaming: #5409

[SparkQA]

Test build #30139 has finished for PR 5486 at commit 5060e6b.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • s" /mesos-home/bin/spark-class $
  • s"cd test-app-1*; ./bin/spark-class $
• This patch does not change any dependencies.

[rxin]

Jenkins, test this please.

[SparkQA]

Test build #30146 has finished for PR 5486 at commit 22014fc.

• This patch fails Scala style tests.
• This patch merges cleanly.
• This patch adds no public classes.
• This patch does not change any dependencies.

[rxin]

Jenkins, test this please.

[SparkQA]

Test build #30148 has finished for PR 5486 at commit 01683de.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.
• This patch does not change any dependencies.

[rxin]

Jenkins, retest this please.

[SparkQA]

Test build #30149 has finished for PR 5486 at commit 01683de.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.
• This patch does not change any dependencies.

[SparkQA]

Test build #30154 has finished for PR 5486 at commit 01683de.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.
• This patch does not change any dependencies.