Refactor: move conn_cleanup to conn_close
Refactor: move conn_cleanup to conn_close

The method was only called from conn_close, and contained
code which isn't strictly needed (resetting variables) as the
object is about to be deleted.

Change-Id: If8d1655866a04511bfc0f500dc3928012c46f972
Reviewed-on: http://review.couchbase.org/87315
Reviewed-by: Dave Rigby <a09264da4832c7ff1d3bf1608a19f4b870f93750@couchbase.com>
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>

daverigby/kv_engine,daverigby/kv_engine,daverigby/kv_engine,daverigby/kv_engine