Refactors setting status into its own top-level function to make it
easier to ensure we _always_ set the status if it's changed on every
reconcile. Previously, it was possible to have stale status if some
earlier part of the provision logic failed.
Updates #16327
Change-Id: Idab0cfc15ae426cf6914a82f0d37a5cc7845236b
Signed-off-by: Tom Proctor <tomhjp@users.noreply.github.com>