Allow callbacks to update their list of workers
Allow callbacks to update their list of workers

We need this to be able to allow coordinators to replace nodes that are
in maintenance mode.

BugzId: 22729

fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb