Tweaks to get vogar runs working after enso move.

- Use ART_TEST_ANDROID_ROOT for the dex locations, so that
  ART can find resources.
- Use the pre-compiled boot image to avoid b/26320300.
- Add new failures to failures file.

bug:26320300

Change-Id: I08653b563f837a7ac3a014424951417f6bdd3294
4 files changed