Currently transfer service isn't aware of configurations of hosts directory and
ctr's `--hosts-dir` doesn't work.
This commit fixes this issue by using `config.ConfigureHosts` instead of
`docker.ConfigureDefaultRegistries`.
This commit also fixes ctr to use this feature for "--hosts-dir" flag.
Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>
7a3b7fba59