With cb80286a4a, the helper function
stringify_ansible_playbook_command was also applied on the
`raw_arguments` content, which is not wanted. Given that users have used
the `raw_arguments` option as a workaround to avoid the bug GH-6726,
this new change ensure that any `--extra-vars` option passed as a raw
argument won't be additonally enquoted by the ansible_local
provisioner.
This change also improves the ansible remote provisioner verbose output,
but has no impact on its behaviour, which was already correct.
Note that this refactoring introduces some code duplications that are not
very elegant (see ansible_playbook_command_for_shell_execution in
host.rb and execute_ansible_playbook_from_host in base.rb). I hope we
can find a better implementation later, but it is good enough for now
since all these parts are covered by corresponding unit tests (the
`ansible_local` stuff being tested via the verbose output of the ansible
remote provisioner).
ab036ddd0b