Image signed without security counter does not get erased if anti rollback protection is enabled

[Karambite]

If MCUboot sees an image that is signed without a security counter, it verifies but does not jump to application, which seems correct, but it does not erase the image.

Unless there is a specific reason to keep this image, an image that mcuboot rejects should not remain in flash.

[nordicjm]

Does not look valid, since the upgrade slot is erased as per https://github.com/mcu-tools/mcuboot/blob/main/boot/bootutil/src/loader.c#L2387