MB-11642: Allow changes to tap/dcp batch size

Based on the type of connection we want to be able to change the
batch size in order to prioritize one connection over the other.

Change-Id: I39789eb63743ee7b3735df1a61f5289e9ddd321b
Reviewed-on: http://review.couchbase.org/41757
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>
Merge remote-tracking branch 'membase/3.0.1'

* membase/3.0.1:
  MB-11642: Allow changes to tap/dcp batch size

Conflicts:
	daemon/memcached.c

Change-Id: I02d87cf5873fac988597895f9ffb1cfe742463f8