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_WALLET_WALLET_H
#define BITCOIN_WALLET_WALLET_H
#include <amount.h>
#include <outputtype.h>
#include <policy/feerate.h>
#include <streams.h>
#include <tinyformat.h>
#include <ui_interface.h>
#include <utilstrencodings.h>
#include <validationinterface.h>
#include <script/ismine.h>
#include <script/sign.h>
#include <util.h>
#include <wallet/crypter.h>
#include <wallet/coinselection.h>
#include <wallet/walletdb.h>
#include <wallet/rpcwallet.h>
#include <algorithm>
#include <atomic>
#include <map>