Use provided sasl credentials to the data nodes

Change-Id: I9d53bb4274dc8344e6647434b23f07fe8b3558ef
Reviewed-on: http://review.couchbase.org/28431
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Reviewed-by: Matt Ingenthron <matt@couchbase.com>