Regularly run tests to monitor workstation configuration state

[emkll]

We run configurations tests on the securedrop-workstation as part of the test make target, but it could be useful to run these periodically (perhaps at boot), to provide some sort of healthcheck for the workstation.

These tests could also be run at boot or as part of the daily cron job, so that we ensure the configuration is as expected, after running provisioning scripts. https://github.com/freedomofpress/securedrop-workstation/blob/dff840b0a4661efaef5459fbb94c05fc7d1f35e5/dom0/securedrop-update#L53

We could also either report or take action on misconfigurations.