Make sure upr control message is properly written to the network

This commit resolves two issues. One issue was that we were not
adding an io vector for the data to be sent and the other issue
was that the key length should be converted to network order as
a short and not a long.

Change-Id: I851b2da6382e3f25ffbec3744f38cb4931e0964b
Reviewed-on: http://review.couchbase.org/35390
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>