Revert "Make OpenJDK 8 the default"

Reverting until all continuous builds that cover branches downstream of master can be updated to use JDK 8.

This reverts commit 1bd16b67c4b05f9df1f6d9ef85365929df0c34ef.

Change-Id: Icb0daa440a6286e07d3cfd9ff8b082b4154ebc21
3 files changed