delete: true - Does not delete file marked for deletion

When adding `delete: true` to the `.sync.yml` the file and running `pdk convert` the file is not deleted.

Steps to reproduce
--------------------------
1) Ensure 'NOTICE' file exists within the module root directory
2) Populate the `.sync.yml` file with NOTICE: delete: true (At the bottom I have included the specific `.sync.yml` file I have used
3) Run `pdk convert' (with flag N)
4) Confirm module has not been converted
5) Inspect the convert_report.txt file
6) Confirm the report does not mention NOTICE being removed
7) Actually run the convert this time: `pdk convert` (with flag Y)
8) Confirm `NOTICE` file still exists

• Note I have also tried to delete metadata.json for testing purposes.

Expected Results
-----------------------
I would expect the report to notify me that NOTICE file will be deleted, I would then also expected the NOTICE file to be deleted when I actually run the convert.

Actual Results
---------------------
The file marked for deletion is not mentioned in the convert_report.txt and then when actually running the convert, the file is not deleted.

Example of .sync.yml I was used (for netdev_stdlib module):

---

.travis.yml:

  bundle_args: --without system_tests

  docker_sets:

    - set: docker/centos-7

      options:

    - set: docker/ubuntu-14.04

      options:

  docker_defaults:

    bundler_args: ""

  secure: ""

  branches:

    - release

  extras:

    - env: CHECK=release_checks

      rvm: 2.1.9

Gemfile:

  required:

    ':development':

      - gem: puppet-blacksmith

        version: '~> 3.4'

      - gem: 'rspec-puppet'

NOTICE:

  delete: true

The output convert_report.txt has been attached.