ensure filesize of deb is included in the hashes list

ensure filesize of deb is included in the hashes list

Filesize is a silly hash all by itself, but in combination with others
it can be a strong opponent, so ensuring that it is in the list of
hashes and hence checked by the normal course of action the acquire
process takes is a good thing.

(cherry picked from commit 5da51e0e2da3f055306562d38103b06a23d81719)