Revert "Revert "Soft-delete all per-node keys from config when shunning a node.""

This reverts commit a1050356cf48a064cfeda2491e11f192952d22f2.

Change-Id: I2ef2dc0f6ea803677661be5fe9cf81fe1bd7b2e1
Reviewed-on: http://review.couchbase.org/36019
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Artem Stemkovski <artem@couchbase.com>