Add missing free()

Change-Id: Ia29a5c4b613eb29f4ec9606d5b715842f465677b
Reviewed-on: http://review.couchbase.org/26293
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Brett Lawson <brett19@gmail.com>