Code review comment for lp:~smoser/curtin/trunk.use-smtar

After merging https://code.launchpad.net/~smoser/curtin/install-from-url/+merge/277482
we're now installing from a url. That url is gzip compressed, so smtar would be used.

One thing i'd like to do is to be able to run the tests with a install from .tar also.

the reason would be that on a local system, installing http://host.ip/foo.tar does uncompressed transfer through virtio with no decompression cost. while the .tar.gz does compressed transfer at cost of decompress to cpu.