simplewallet: add missing guards/locks for multisig commands

src/simplewallet/simplewallet.cpp

@@ -1161,6 +1161,7 @@ bool simple_wallet::make_multisig_main(const std::vector<std::string> &args, boo
     fail_msg_writer() << tr("wallet is watch-only and cannot be made multisig");
     return false;
   }
+  CHECK_IF_BACKGROUND_SYNCING("cannot be made multisig");
 
   if(m_wallet->get_num_transfer_details())
   {
@@ -1270,6 +1271,8 @@ bool simple_wallet::exchange_multisig_keys_main(const std::vector<std::string> &
       return false;
     }
 
+    LOCK_IDLE_SCOPE();
+
     try
     {
       std::string multisig_extra_info = m_wallet->exchange_multisig_keys(orig_pwd_container->password(), args, force_update_use_with_caution);