CCBC-433 A new randomization algorithm.

Now using a Fisher–Yates shuffle to randomize the host list.

Change-Id: I03ccffdaedfcfe52f5fbddb367657fc8e0c76074
Reviewed-on: http://review.couchbase.org/37706
Reviewed-by: Dave Rigby <daver@couchbase.com>
Reviewed-by: Mark Nunberg <mnunberg@haskalah.org>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
CCBC-435: retrieve command _after_ "purge_implicit_responses"

Change-Id: I126f7ef350cb983567ef923d33c83c43b8ca24d8
Reviewed-on: http://review.couchbase.org/37712
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>