HTTP is a fun protocol.
Size is basically optional. And clients implicitly trust the server
and socket has transferred all the bytes. Which *really* means you
should always checksum.
But... previously we didn't checksum as part of retrying.
So if anything happened with python-requests, or lower level
library code or the system itself causing bytes to be lost off the
buffer, creating an incomplete transfer situation, then we wouldn't
know until the checksum.
So now, we checksum and re-trigger the download if there is a
failure of the checksum.
This involved a minor shift in the download logic, and resulted in
a needful minor fix to an image checksum test as it would loop for
90 seconds as well.
Closes-Bug: 2038934
Change-Id: I543a60555a2621b49dd7b6564bd0654a46db2e9a
cb61a8d6c0