Refactor: Use helper function to perform allocations
Refactor: Use helper function to perform allocations

We've got wrappers in memcached.h to support allocation
through the engine API. We're going to extend the
allocation pattern to support "privileged" or "system internal"
bytes which may exceed the item limit, and it is easier (and
cleaner) to do this if everyone goes through the same
wrappers.

Change-Id: Ibde5b94d0023b81029bc1d21d6e529e2b428e9b1
Reviewed-on: http://review.couchbase.org/71464
Reviewed-by: Dave Rigby <a09264da4832c7ff1d3bf1608a19f4b870f93750@couchbase.com>
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>

daverigby/memcached,couchbase/memcached,couchbase/memcached,daverigby/memcached,daverigby/kv_engine,daverigby/kv_engine,daverigby/memcached,daverigby/kv_engine,couchbase/memcached,daverigby/memcached,daverigby/kv_engine,couchbase/memcached