MAR-218: Switch to using task imports instead of includes:

- Should result in somewhat faster run, except the includes happen
during planning phase. None of the changed includes will have
problem with this.
- Solves the issue of (included) imported tasks not being tagged
properly, particularly in relation to the mechanism for explicitly
running all handlers.

MAR-218: Switch to using fully-qualified collection names for all tasks:

- Ensures there is no ambiguity when invoking a module.

MAR-218: Quote all octal values in YAML files:

- Fixes linting errors, and ensures there is no ambiguity in case of
YAML specification changes.

MAR-218: Update noqa directives for ansible-lint to use text tags:

- Numeric tagging is deprecated.

MAR-218: Fix include invocations:

- The old include keyword/task has been deprecated in favour of more
explicit include_tasks one.

MAR-232: Switch to using IP addreses in firewall rules for mail_forwarder role:

- Perform lookups on managed machine for the passed-in SMTP relay
host, and use those values when populating the firewall rules.

MAR-151: Drop rcconf workaround:

- The workaround was needed on Debian Jessie because the systemctl
is-enabled command did not behave correctly for SysV init scripts.
- Drop the installation of the rcconf package.
- Use the "enabled" parameter in service module instead.

MAR-148: Fixing linting errors:

- Do not compare against booleans when value is already boolean in
"when" conditions.
- Do not compare variables to empty strings in "when" conditions. This
change currently works only for complex variables (stuff can break
badly in case of simple variables in current default Ansible
configuration).

MAR-148: Fixing linting errors:

- Do not compare against booleans when value is already boolean in
"when" conditions.
- Use pipefail in conjunction with setting the shell to Bash when
extracting the backup encryption key IDs.
- Do not compare variables to empty strings in "when" conditions. This
change currently works only for complex variables (stuff can break
badly in case of simple variables in current default Ansible
configuration).
- Fix missing space in one of Jinja2 templates.

MAR-135: Switch to using run_handlers instead of handlers as variable:

- Updated all roles to now depend on run_handlers being set to True in
order to force execution of handlers.

MAR-129: Updated mail_forwarder role for new Ansible and Molecule versions:

- Moved variables out of test playbook into group_vars.
- Fixed linting issues.
- Use top-level linting configuration file in tests.
- Updated how the hosts are referenced when executing the tests.

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: Update mail_forwarder role/tests:

- Install swaks on mail-server instance for testing SMTP.
- Install procmail via mail_forwarder role (needed to be explicit for Debian
Stretch).
- Introduce small sleep when mails are sent to localhost for delivery to remote
hosts before checking the logs in order to allow Postfix to process the
queue.

MAR-27: Implemented tests for mail_forwarder role:

- Install hping3 (for testing connectivity) on mail-server test machine.
- Changed syntax used for deploying the SMTP relay truststore in order to ensure
that tabs are preserved.
- Implemented tests for the mail_fotwarder role.
- Updated tests for mail_server role to check for new setting
added (smtp_host_lookup).

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.