set_firewalld_default_zone: add a bash remediation

[nightmared]

Hello, this bash remediation for set_firewalld_default_zone switches all the network zones to the drop firewalld zone.
Note that this may be dangerous on a running system, as one could lock oneself out of its own system.

I'm more than open to discussions on whether that should be dropped (in which case the whole OVAL check + bash remediation) could probably be replaced by a simple call to the line_in_file template.

[openshift-ci]

Hi @nightmared. Thanks for your PR.

I'm waiting for a ComplianceAsCode member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[github-actions]

Start a new ephemeral environment with changes proposed in this pull request:

rhel8 (from CTF) Environment (using Fedora as testing environment)

Fedora Testing Environment

Oracle Linux 8 Environment

[github-actions]

This datastream diff is auto generated by the check Compare DS/Generate Diff

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New data stream adds bash remediation for rule 'xccdf_org.ssgproject.content_rule_set_firewalld_default_zone'.

[codeclimate]

Code Climate has analyzed commit e45b198 and detected 0 issues on this pull request.

The test coverage on the diff in this pull request is 100.0% (50% is the threshold).

This pull request will bring the total coverage in the repository to 58.5%.

View more on Code Climate.

[nightmared]

As is shown in #11250 (comment), work is needed to decide a better shape for this feature.
I will close this for now, and open a new PR when a sane behaviour has been agreed upon in that discussion.

Sorry for the spam :/