Temporary - changes for branch-2.2.0

[dazza-codes]

Throwing this up to temporarily evaluate the diffs; make no promise that I have time to resolve any conflicts. The spark-2.2.0 branch served the purpose for our POF demo project, no idea whether I'll come back to it.

If I can't get back to it, feel free to cherry-pick from it. We didn't need hadoop/tachyon, so it was carved out, but that's likely to stay here on the main repo. Had some difficulties updating hadoop with spark 2.2.x and didn't bother to resolve it.

[nchammas]

You don't need to submit a PR just to review the diff between your branch and upstream. You can directly compare branches on GitHub, even across repos.

Here's the diff you're looking for: https://github.com/amplab/spark-ec2/compare/branch-1.6...darrenleeweber:spark-2.2.0

If this PR serves no other purpose, please close it.

(For those wondering when/if spark-ec2 will update its AMIs and support Spark 2.2, please see this comment.)