These tasks are conditional and mutually exclusive due to the "when"
clause. Using import_tasks means that these are imported before the
playbook execution and then skipped during evaluation of the test.
It makes sense in this case to use include_tasks so that the tasks
are only imported during playbook execution if the condition is met.
Ansible 2.4 changes the way includes work. Now you have to use "import"
for playbooks and tasks that are static, and "include" for those that
are dynamic (ie, those that use variables, loops, etc).
See: http://docs.ansible.com/ansible/devel/playbooks_reuse_includes.html
Debian 9 is still in beta and doesn't have nginx.org builds yet, so
we need to use the nginx package in Debian's repositories, and that
required a bit of a different configuration.
After official nginx.org builds are released we can revert this.
