MB-11352: Don't include the meta section in the packet value size

Any extra meta data will be put into the meta section of the upr
packet.

Change-Id: Ifb0ef037c246f10b1058c3a5f177fe01160073d5
Reviewed-on: http://review.couchbase.org/38030
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>