Fix SettingsRoboTests build error with OpenJDK 9

- CL http://ag/3671365 broke git_pi-release/marlin-userdebug-jdk9
  when building "m checkbuild". It shouldn't break the image build

Test: m SettingsRoboTests
ROBOTEST_FILTER=com.android.settings.datetime.timezone
EXPERIMENTAL_USE_OPENJDK9=true USE_R8=true
Change-Id: I161c0350cff55bd13ba4a6c63df4e4e9bc4b1a5f