Unlink app image if copy fails for A/B OTA

Usually this happens when the app was recompiled with interpret-only.
In this case, move_ab_path will fail for the app image. If this
occurs, delete the existing app image to not have a stale one wasting
storage space.

Test: Make fake AB ota, delete the a/b generated app image, take the
OTA, ensure there is no stale app image after reboot. Also tested
that other apps with valid app images still had an image.

Bug: 31323617
Change-Id: I699b5eb3dc8f82759c284a1d299865b2c3a890d0