(maint) Add global cleanup option for mock stubs

[mckern]

Toggling the cleanup_on_failure option in our mock stubs will make it
easier to diagnose problems with builds by leaving failed builds
staged in their initialized mocks. By default, both options are true
(which is consistent with the defaults as shipped in mock).

[haus]

👍

[MosesMendoza]

Is the intended use case to set some nodes to permanently not clean up in various cases? If not, is the workflow that in order to adjust whether we want the cleanup to occur we have to edit the node definition, commit, PR, merge, for that builder to specify no cleanup? It seems like a lot of work to me.

[MosesMendoza]

Is this intended for PE usage or FOSS or both? This will impact builders that the packaging repo uses, which has its own clean up - https://github.com/puppetlabs/packaging/blob/master/tasks/mock.rake#L209-L211

[mckern]

This only impacts whether or not the contents of the mock build are purged if the build fails. Cleaning up old mocks is still a good idea, but this will leave artifacts like config.log around if a mock dies (or continue to purge the mock build pieces if a build succeeds). PE & FOSS builds don't really matter in this context, just the ability to chroot into a mock and figure out why something fails.

[MosesMendoza]

I see. I was missing the context that we would, after this change, update applications of this module to false for cleanup on failure. 👍

[mckern]

Two thumbs up? I merge!