Perf: Skip zeroing of item_info_holder
Perf: Skip zeroing of item_info_holder

Skip zeroing the item_info_holder struct which is passed into
get_item_info. Only the info.value member actually requires
initializing (to the number of iovecs available); the rest is
unnecessary.

Reduces time in bzero from 1.0% to 0.3% (as measured by OS X
Instruments running pillowfight).

Change-Id: I4f92c49a861b91fde54a50baaa2843800a6b06dd
Reviewed-on: http://review.couchbase.org/52369
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Trond Norbye <60edd2ef23891a753f231b0c6f161dc634079a93@gmail.com>

cloudrain21/memcached-1,cloudrain21/memcached-1,couchbase/memcached,owendCB/memcached,daverigby/kv_engine,daverigby/kv_engine,daverigby/memcached,owendCB/memcached,owendCB/memcached,owendCB/memcached,daverigby/kv_engine,daverigby/memcached,couchbase/memcached,cloudrain21/memcached-1,daverigby/memcached,daverigby/kv_engine,couchbase/memcached,daverigby/memcached,couchbase/memcached,cloudrain21/memcached-1