[SPARK-10275][MLlib] Add @since annotation to pyspark.mllib.random

[yu-iskw]

No description provided.

[SparkQA]

Test build #42192 has finished for PR 8666 at commit e71141d.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • case class Instance(w: Double, a: Vector, b: Double)
  • class WeibullGenerator(
  • class IndexToString(JavaTransformer, HasInputCol, HasOutputCol):

[SparkQA]

Test build #42231 has finished for PR 8666 at commit 6a8817b.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[noel-smith]

All LGTM.

[mengxr]

Merged into master. Thanks!