addmultisigaddress creates an address respecting the setting, being unable to generate a specific type of address without also adding it to the wallet seems wrong.

I suppose in the future `addresstype` may be refactored to be wallet-specific, which would leave this non-wallet rpc call without an argument. Perhaps there should just be an optional parameter to set it.
#ifndef BITCOIN_OUTPUTTYPE_H
#define BITCOIN_OUTPUTTYPE_H
#include <keystore.h>
#include <script/standard.h>
#include <string>
#include <vector>
enum class OutputType {