add log message

lib/server.js

@@ -1081,6 +1081,7 @@ WalletService.prototype.getBalance = function(opts, cb) {
       if (!_.isArray(activeAddresses)) {
         return self._getBalanceOneStep(opts, cb);
       } else {
+        log.debug('Requesting partial balance for ' + activeAddresses.length + ' out of ' + nbAddresses + ' addresses');
         self._getBalanceFromAddresses(activeAddresses, function(err, partialBalance) {
           if (err) return cb(err);
           cb(null, partialBalance);