MAR-163: Attach noqa directives to task names (if skipping is applicable on task level) for better uniformity:

- This way the indentation of comment describing the directive can
always be on the same level everywhere (irrespective of how the rest
of task arguments are listed).

MAR-163: Reformat skip-QA directives for ANSIBLE0012 (Commands should not change things if nothing needs doing):

- Update codes used to identify the disabled QA checks.
- Switch to using new syntax that disables only a specific QA check
instead of all of them on a single task.
- Drop disabling QA checks on two command tasks, since they actually
use the "creates" directive (therefore passing the QA check).

MAR-114: Updated task syntax for mail roles:

- Updated mail_server and mail_forwarder roles.
- Added and removed quoting where it makes sense.
- Switched to using expanded syntax (instead of one-liners).
- Updated ordering of arguments in task definitions.

MAR-27: Added initial scaffolding for testing mail_forwarder role:

- Fixed issues reported by Ansible linting check (some mode-related syntax and
one ignore.
- Added Molecule configuration for testing mandatory and optional
parameters. Covers both Debian Jessie and Debian Stretch.
- Added test playbook for setting-up the test instances. A helper relay mail
server.
- Updated both mail_server and mail_forwarder to fall-back to using
native (/etc/hosts) resolving if DNS fails. Solves issue with test environment
not having proper DNS set-up for all domains etc.
- Added a number of data/config files associated with tests.
- Added dummy test file.