Initialize seqno array with rand()

Change-Id: I8e46e48cf3b279c31476887c6d36a704e90c6a9d
Reviewed-on: http://review.couchbase.org/25075
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>