This change ensures we close all Blobs in the asset/archive logic.
In particular, the archive.Read function returns a map of files to
Blobs and after we are done copying the contents we must ensure
that we invoke Close, otherwise we may leak file handles, sockets,
and so on. This may or may not be the culprit to the "too many
files open" errors we are hitting while deploying the M5 bits.
627d97d83f