Bump mixlib-cli to 2.1.5
Bump mixlib-cli to 2.1.5

This pull request was triggered automatically via Expeditor when mixlib-cli 2.1.5 was promoted to Rubygems.

This change falls under the obvious fix policy so no Developer Certificate of Origin (DCO) sign-off is required.

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