bhavanki Update CM/CDH defaults to 5.15, Spark 2 to 2.3.0.cloudera2
This changeset moves up defaults across Director from 5.14 to 5.15 in
anticipation of the 2.8.0 release. It also bumps up Spark 2 to
2.3.0.cloudera2 where it hasn't already been.

Also, the simple setup configuration files that involve Java 8
installation are updated to point to the upcoming 2.8.0 release
repository.

(cherry picked from commit 5e10a92de0009fd11363cb4f98c35af224932f7b)
Latest commit b88f4a4 May 1, 2018