Fix cg-aws-light-stemcell-builder

[ghost]

This process/pipeline is broken. Builds are failing due to a file glob issue and we also need to remove the conversion to vmdk step that was also removed upstream in https://github.com/cloudfoundry-incubator/aws-light-stemcell-builder/commit/59ac7f7651d5db04b10edf8233dc8fa0abf04629.

• [x] Remove the conversion to vmdk
• [x] General fixes and cleanup

[ghost]

Related to #105

[ghost]

https://github.com/18F/cg-aws-light-stemcell-builder/pull/4

[mogul]

@dlapiduz we're doing work to ensure this is a lighter fork to maintain, but can you verify that it works and can be closed?

[mogul]

Confirmed working.