MB-9855: Retrieve/Regenerate SSL certificate for cluster

Change-Id: I8bcbb52109d033d5a618300a666594c54e7a8222
Reviewed-on: http://review.couchbase.org/31825
Reviewed-by: Steve Yen <steve.yen@gmail.com>
Tested-by: Bin Cui <bin.cui@gmail.com>