Fix the 'ignore-path' config option
Fix the 'ignore-path' config option

The option shouldn't be named 'ignore_path' but should be
named 'ignore-path' to match the docs and to match the CLI
argument.

Change-Id: If5346910b259a0c092eea5c9adde281c2f2ff347

doismellburning/doc8,stackforge/doc8,openstack/doc8,tschuy/doc8