CBQE-0: uprbase.load_buckets() needs bucket auth

set default bucket/password for load bucket

Change-Id: Ied2e6885764b5df09928ae6d07dfd96ef7b5f73f
Reviewed-on: http://review.couchbase.org/40120
Reviewed-by: Tommie McAfee <tommie@couchbase.com>
Tested-by: Tommie McAfee <tommie@couchbase.com>