Allow operation to modify the config nodes

This should allow the nodes to be modified before bootstrap. It may also
be used to modify the nodes after bootstrap but has not been tested.

Change-Id: I222f0d148ffc0233af9d085c745e05a8ea2c158b
Reviewed-on: http://review.couchbase.org/34000
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>