Combine determining blob properties and validating against submitted values
Combine determining blob properties and validating against submitted values

... primarily to make blobDigest available earlier; reusing some of the
comparisons isn't really that important.

Should not change behavior.

Signed-off-by: Miloslav Trmač <9c008e38982a5397deb855345fb164f0558459ae@redhat.com>

containers/image,containers/image