Convert operation handling to mcreq

This removes a lot of the older packet stuff

Change-Id: Icb2cc7731e7c655145a81dfa15baad80f34287a1
Reviewed-on: http://review.couchbase.org/34600
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>