(PUP-778) Add yumrepo acceptance smoke test

[johnduarte]

This commit adds an acceptance test for the yumrepo resource. It
verified that yumrepos can be ensured both present and absent and
that they are then visible as yumrepo resources.

[puppetcla]

CLA signed by all contributors.

[hlindberg]

Triage Notes:

• Can this be an integration test instead? (acceptance tests should only be used if it is impossible to test with an integration or unit level test)
• @joshcooper the yumrepo type has a target parameter, you can run a puppet apply and add the target parameter and assert that the right files are created - say comparing to a fixture.
• ping @johnduarte

[peterhuene]

PR triage notes: waiting on @johnduarte for feedback. Is this a test coverage hole currently in specs?

[joshcooper]

PR Triage Notes:

• @johnduarte @er0ck wondering if you've had a chance to review this PR and see what can be implemented as integration tests?

[er0ck]

closed in favor of future work in PUP-3886