SPY-175: Reduce memory use in binary GET

Change-Id: I9b90aab0b54a2ae7d2c262d499ff47482b9d6c6c
Reviewed-on: http://review.couchbase.org/38359
Reviewed-by: Michael Nitschinger <michael.nitschinger@couchbase.com>
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>