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.
#include <outputtype.h>
#include <keystore.h>
#include <pubkey.h>
#include <script/script.h>
#include <script/standard.h>
#include <assert.h>
#include <string>
static const std::string OUTPUT_TYPE_STRING_LEGACY = "legacy";
static const std::string OUTPUT_TYPE_STRING_P2SH_SEGWIT = "p2sh-segwit";
static const std::string OUTPUT_TYPE_STRING_BECH32 = "bech32";
bool ParseOutputType(const std::string& type, OutputType& output_type)