Revert "Revert "Enable chained vbmeta for boot""

This reverts commit 8ed24f1c7f8923e0b0ac62c16abc5ea32c1a11e0 which
disables chained vbmeta for boot.

Bug: 176930600
Test: manually verify chained vbmeta is enforced
Change-Id: Iba79a072798ff4dd0eb9add3c36d7f6c1ffb4655
2 files changed