This reverts commit 1f4fb1d7a5.
This unfortunately wasn't actually tested. Because the image-based
tests run sequentially, a prior failure in the centos-8 job meant the
ubuntu job never ran.
This is failing with
10-cache-ubuntu-tarball: line 28: DIB_LOCAL_IMAGE: unbound variable
There is also a seemingly unused variable DIB_IMAGE_LOCAL_FILE; I'm
not sure what this is doing.
For now revert, and it can be re-proposed with appropriate testing.
Change-Id: I0f3897c90dc863ee04c3295b9cb094f02d8658e3
d5fa64325f