I have a case where a user provided the checksum URL with SHA256
checksums, while Metal3 defaulted os_hash_algo to "md5". We're going
to change the Metal3 defaults in the next API version, but for now let
us issue a clear warning in such case.
Closes-Bug: #2085331
Change-Id: Ie4e62a378dc4a2089944f4302df3a8671b7c960f
(cherry picked from commit d8d32d93bd9fd0a9e759f7babe5db6fa804626de)
(cherry picked from commit aa01777ca8e4de7822bd8263ad85a0669bafbf55)