
Threading is prone to database lock exceptions when using the default database backend (sqlite) and so disable it by default. Users can enable threading when using mysql or postgresql by specifying the ARA_CALLBACK_THREADS environment variable or callback_threads in ansible.cfg. Fixes: https://github.com/ansible-community/ara/issues/195 Change-Id: I80edfd6268684722c2783e01323355d791c19b9d