SPARK-3962 Marked scope as provided for external projects.

Somehow maven shade plugin is set in infinite loop of creating effective pom.

Author: Prashant Sharma <prashant.s@imaginea.com>
Author: Prashant Sharma <scrapcodes@gmail.com>

Closes #2959 from ScrapCodes/SPARK-3962/scope-provided and squashes the following commits:

994d1d3 [Prashant Sharma] Fixed failing flume tests
270b4fb [Prashant Sharma] Removed most of the unused code.
bb3bbfd [Prashant Sharma] SPARK-3962 Marked scope as provided for external.
[DOC][PySpark][Streaming] Fix docstring for sphinx

This commit should be merged for 1.2 release.
cc tdas

Author: Ken Takagiwa <ugw.gi.world@gmail.com>

Closes #3311 from giwa/patch-3 and squashes the following commits:

ab474a8 [Ken Takagiwa] [DOC][PySpark][Streaming] Fix docstring for sphinx