[GH-234] Use stock Debian Stretch, not the Dokken version
[GH-234] Use stock Debian Stretch, not the Dokken version

The Dokken image includes a number of packages not everyone has,
and hence the bug with dirmngr

Signed-off-by: Tom Parker <9cbd9c1da67dd4d9d0281b342ba534e921fabeed@tevp.net>

opscode-cookbooks/apt,opscode-cookbooks/apt,chef-cookbooks/apt,chef-cookbooks/apt