Converts grsecurity config tests Serverspec -> TestInfra
Converts grsecurity config tests Serverspec -> TestInfra

Parametrization of the `paxtest` command slows down the test run
significantly, but it's currently disabled by default due to lack of the
`paxtest` command. We should update the app-test role to install paxtest
to make sure it's available on staging hosts.

Setting the PaX flag checks as permissible failures due to PaX flags
being out of sync between:

  * Ansible playbook in SD repo
  * post-install kernel hook in securedrop-grsec metapackage

The Ansible config should be updated so that the flags match.

ehartsuyker/securedrop,ageis/securedrop,garrettr/securedrop,conorsch/securedrop,ehartsuyker/securedrop,heartsucker/securedrop,ehartsuyker/securedrop,ageis/securedrop,conorsch/securedrop,heartsucker/securedrop,conorsch/securedrop,micahflee/securedrop,conorsch/securedrop,garrettr/securedrop,heartsucker/securedrop,micahflee/securedrop,ehartsuyker/securedrop,heartsucker/securedrop,micahflee/securedrop,ageis/securedrop,conorsch/securedrop,micahflee/securedrop,garrettr/securedrop,heartsucker/securedrop,ehartsuyker/securedrop,ageis/securedrop,garrettr/securedrop,ehartsuyker/securedrop