Revert "Make sure the cache lookup returns always the same result"

This reverts commit 1d4b7d8fa1af95ce83f263a49ed24e686fa7cb62.

Docker-DCO-1.0-Signed-off-by: Sjoerd Langkemper <sjoerd@byte.nl> (github: Sjord)
Fix issue #3375 - Return most recent image from the cache

ImageGetCached searches for an image from the cache. Instead of returning the
first image it finds, it should return the most recently created image. When a
build with --no-cache then adds a new image with the same parameters, it is
used instead of the old, existing image.

Docker-DCO-1.0-Signed-off-by: Sjoerd Langkemper <sjoerd@byte.nl> (github: Sjord)