The default behavior of the dpkg DIB element is to overlay a
directory from the host filesystem at /var/cache/apt/archives in the
chroot so that the cache of packages can persist to subsequent image
builds. This has a side effect of not actually populating the cache
within the chroot at all. Disable the local cache on the host so
that we can cache DEB packages in our images.
Change-Id: I1e33cb2e6049c83b3aad4a18885d8bd909f09195
d3cc7c21ea