properly set ansible_python_interpreter for local task execution

this works a limitation in ansible for connection: local and makes it so
that you can run connection: local playbooks with a /usr/bin/python that
is Python3 and an Ansible virtualenv that is Python2

see: https://github.com/ansible/awx/issues/3267

awx/main/management/commands/create_preload_data.py

@@ -47,7 +47,7 @@ class Command(BaseCommand):
                                              created_by=superuser)
                 Host.objects.create(name='localhost',
                                     inventory=i,
-                                    variables="ansible_connection: local",
+                                    variables="ansible_connection: local\nansible_python_interpreter: '{{ ansible_playbook_python }}'",
                                     created_by=superuser)
                 jt = JobTemplate.objects.create(name='Demo Job Template',
                                                 playbook='hello_world.yml',