iofactory.c: preserve cookie in options_from_info

Change-Id: I81d230c6cec30d4a477d44fe1b43a50b1896c719
Reviewed-on: http://review.couchbase.org/28548
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Reviewed-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>