Display Cyan error message instead of Red when ignoring errors.

Some tasks are designed to fail under certain conditions and the play should continue as described here:
http://docs.ansible.com/playbooks_error_handling.html

Ansible provides the 'ignore_errors' field you can set to 'yes'. The problem is that Ansible currently still displays a Red error message in this case, which is visually distracting and causes the impression to a casual observer that something went wrong. This change in the on_failed() callback checks if ignore_errors is True and if so displays the error message in Cyan, which is the color of the 'ignoring...' message.