[SPARK-18613][ML] make spark.mllib LDA dependencies in spark.ml LDA private

[sueann]

What changes were proposed in this pull request?

spark.ml.*LDAModel classes were exposing spark.mllib LDA models via protected methods. Made them package (clustering) private.

How was this patch tested?

build/sbt doc  # "millib.clustering" no longer appears in the docs for *LDA* classes
build/sbt compile  # compiles
build/sbt
> mllib/testOnly   # tests pass

[srowen]

I get it, but making something less visible after it's released is also a breaking change. Without a good reason for that we shouldn't make changes like this.

[jkbradley]

@srowen This actually isn't a breaking change. This is making protected methods private within classes which cannot be extended outside of Spark. The classes are not final, but they only provide private constructors.

[srowen]

Oh, the class is private already, right on. That seems OK then.

[jkbradley]

@sueann Try running dev/mima locally. I bet you'll have to add stuff to the MiMaExcludes.scala file b/c of false positives.

@srowen Yep, I'm sometimes thankful for our paranoia about making things too public!

[SparkQA]

Test build #72607 has finished for PR 16860 at commit ce8abb3.

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

[jkbradley]

LGTM
Merging with master
Thanks @sueann !