MB-11711: Don't log get errors for failed meta only gets

Failures for these are expected since we are checking to see if a
deleted item exists. As a result these should not be logged.

Change-Id: I40825d6a3cb780b647be258faeb9bc5e3ae99095
Reviewed-on: http://review.couchbase.org/39356
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>
Notify checkpoint creation events to paused UPR conns

- Notify these events to corresponding paused upr
connections along with tap connections.

Change-Id: I0c820c48953f63d590a7538041ae68b1b382a251
Reviewed-on: http://review.couchbase.org/39367
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: abhinav dangeti <abhinav@couchbase.com>
MB-11592: Use a queue_item in a MutationResponse instead of and Item

This will allow us to pull queued_items out of the CheckpointManager
and into and ActiveStream without adding any memory overhead. This
also simplified the cleanup of a MutationResponse because we no
longer need to seperately delete the item contained inside this
class.

Change-Id: I0fc67ac66da6bd0c0ad0cd0369ee0a377d2b3bd9
MB-11592: Create snapshots when getting items from the chk queues

Change-Id: I8a262eb7856c97e11e95570fbdaef82f3f79054a
MB-11721: Send acks for snapshot markers during the takeover phase

By sending acks for snapshot markers we can make sure that all items
hve actually been processed on the new master before sending any
set vbucket state messages. This change will reduce the time that
a vbucket might be unavailable due to state changes.

Change-Id: I70b64035c4684754bfcdb632f29cb83fecf161a1