Set the default ansible logging to log to a file

[Kevin Carter]

The ansible.cfg file should be used to set the logging for all ansible activity when using the `os-ansible-deployment system`. The entry goes in the "defaults" section and is defined as such:

[defaults]
log_path = /var/log/ansible.log

I propose that the option be set to the running users home folder by default and that when executing the `gate-commit-check.sh` script we set it to log to the ``/openstack/aio1/ansible.log``. In this way we can collect ansible logging data upon completion of the gate job and deployers have access to the same data in their regular home folder.

[Jesse Pretorius (jesse-pretorius)]

Currently only implemented for the gate check: https://github.com/stackforge/os-ansible-deployment/blob/master/scripts/bootstrap-aio.sh#L45-L49