cts-tradefed: Update java version check.

 - Only allow versions 1.8 or 9; earlier versions are no longer
   supported.
 - Drop the check for an unset EXPERIMENTAL_USE_OPENJDK9, since
   the semantics of that are about to change.

Note: For users who checked out the Android source tree and run
lunch, the correct version of java is always added to the path
through the bundled OpenJDK binaries.

Test: Treehugger
Test: Checked that cts-tradefed doesn't immediately exit with
      a version error (with OpenJDK 8 or 9 binaries on the PATH)
Test: Ran the following command in terminals with OpenJDK 8 and 9
      java on the PATH and verified that it produced a nonempty
      output:
java -version 2>&1 | head -n 1 | grep 'version [ "]\(1\.8\|9\).*[ "]'

Bug: 69449021
Change-Id: Ib86e2ae460b3b7e49d6a58631a92fd004728b4c8
1 file changed