Remove Ubuntu 14.04 from the build pipeline
Remove Ubuntu 14.04 from the build pipeline

Ubuntu 14.04 is EOL and we should stop building / testing packages for
it. Instead we'll build on Ubuntu 16.04 and test those packages on 16.04
and 18.04.

Signed-off-by: Tim Smith <764ef62106582a09ed09dfa0b6bff7c05fd7d1e4@chef.io>

chef/chef-dk,chef/chef-dk,chef/chef-dk