Remove post-install verification

post-install verification calls range_sha1() and checks if the given
partition has expected contents. It takes roughly 20 seconds on
angler with 2.8G system image. Remove it to speed up OTA update. Also
abort the update if block_image_update() fails, as we were relying on
post-install verification to capture block_image_update() failures.

Bug: 27729678
Change-Id: I8123cd8929295ec26df247acf6bb51df813771d9