Generic way to configure clean step priorites feature
( https://review.opendev.org/c/openstack/ironic/+/744117 ) enabled support
for customising clean step priorities for any clean step by setting a
configuration option. However, due to an error in code, it was not possible
to use this feature to enable/disable steps entirely using this option
as overrides were applied too late, after the disabled steps were already
filtered out.
This change fixes this error, making it possible to use step priority
override configuration option to enable/disable steps as required.
Story: 2009105
Change-Id: If3c01e6e4e8cedfe053e78fab9632bfff3682b06
71481ac483