Bump knife-ec2 to 1.0.28
Bump knife-ec2 to 1.0.28

This pull request was triggered automatically via Expeditor when knife-ec2 1.0.28 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