Use clean_file to prevent duplicates entries in securedrop_workstatio…

…n.list

fpf-apt-test-repo.sls would append the repo URL to /etc/apt/sources.list.d/securedrop_workstation.list each time make * is called. This is because templates persist accross installs, and the source is added to the template. Using `clean_file: True` will ensure `/etc/apt/sources.list.d/securedrop_workstation.list` is squashed each time fpf-apt-test-repo.sls is invoked.

dom0/fpf-apt-test-repo.sls

@@ -29,6 +29,7 @@ configure apt-test apt repo:
     - name: "deb [arch=amd64] https://apt-test-qubes.freedom.press stretch main"
     - file: /etc/apt/sources.list.d/securedrop_workstation.list
     - key_url: "salt://sd/sd-workstation/apt-test-pubkey.asc"
+    - clean_file: True # squash file to ensure there are no duplicates
     - require:
       - pkg: install-python-apt-for-repo-config