Keep openstack mapping_path option
Keep openstack mapping_path option

Removal of this option breaks backwards compatibility

When we moved the openstack actions to mistral-extra this
option was removed. This adds it back if mistral-extra is
installed otherwise it keeps the same

Change-Id: I3dbf26e3fdf2d2bd17d99b678172bd9ac02a7323
Closes-bug: #1866621

openstack/mistral,openstack/mistral