Add a "--force" argument to "bin/config done"
Ref T11922. When we deploy on Saturday I need to rebuild all the cluster indexes, but some instances won't have anything indexed so they won't actually trigger the activity.
Add a --force flag that just clears an activity even if the activity is not required.
Test Plan: Ran bin/config done reindex --force several times.
Reviewed By: chad
Maniphest Tasks: T11922
Differential Revision: https://secure.phabricator.com/D16970