Add piece file size checking to check-deals

[linuskendall]

check-deals retrieve the piece sizes reported fro mthe upstream.

we should be able to cross reference that to the piece sizes that we expect from metadata.yml.

if they don’t match that’s probably an error.

[gagliardetto]

We actually don't know the real piece size. It doesn't seem to be saved anywhere, or the data that we have is wrong.

The actual size of the pieces doesn't match ANY of the numbers we have.

[gagliardetto]

example:

piece 1/5: size_from_http=34091302912, padded_size=34359738368, content_size=30000000017, header_size=26
piece 2/5: size_from_http=34091302912, padded_size=34359738368, content_size=30000000012, header_size=26
piece 3/5: size_from_http=34091302912, padded_size=34359738368, content_size=30000000385, header_size=26
piece 4/5: size_from_http=34091302912, padded_size=34359738368, content_size=30000000327, header_size=26
piece 5/5: size_from_http=34091302912, padded_size=34359738368, content_size=21844758426, header_size=26