ANDROID: AVB: Only invalidate vbmeta when told to do so.

ANDROID: AVB: Only invalidate vbmeta when told to do so.

When using AVB, the dm-verity error handling mode is now customizeable
by the bootloader. This CL is for the kernel-side support - it makes
the AVB error handler invalidate the vbmeta partition only if
androidboot.vbmeta.invalidate_on_error is set to "yes".

Bug: 38157502
Test: Manually tested all dm-verity error modes on UEFI-based bootloader.
Change-Id: If36b8a5be9ffd6120e7e0c162843e732eba2ce26
Signed-off-by: David Zeuthen <zeuthen@google.com>