Add test coverage for ansible_local provisioner

[gildegoma]

Context: For refactoring safety on the ansible provisioner, the introduction of ansible_local has been made without major changes in the unit test parts. The downside: unit tests should also be refactored to ease the coverage of both ansible provisioners.

See #2103, #5340 and #6500

Goal:

Keep codebase stable after release 1.8.0, and introduce a new set of unit tests covering both provisioners before accepting new changes.

See http://betterspecs.org/

Tasks:

• [x] config parts
• [ ] provisioner parts
• [ ] cap parts of the ansible_local provisioner (80% done via #11265, Tests for RHEL and Fedora are still pending)
• [ ] other parts?

Related Issues:

• 6726 (Handling of extra_vars as a Hash is not covered by in the ansible provisioner unit tests)

• 6570 (Switch to Ansible 2.x arguments and variables naming)

• 7195

• 11227

[gildegoma]

Unit Test coverage is added for cap code via #11227