FROMLIST: bootstd: android: Allow boot with AVB failures when unlocked

When the bootloader is UNLOCKED, it should be possible to boot Android even if AVB reports verification errors [1].

This allows developers to flash modified partitions on userdebug/engineering builds.

Developers can do so on unlocked devices with:

$ fastboot flash --disable-verity --disable-verification vbmeta vbmeta.img

In such case, bootmeth_android refuses to boot.

Allow the boot to continue when the device is UNLOCKED and AVB reports verification errors.

Bug: TIAU-545

/cc @glaroque @mfournier @nkbelin