add support of batch calls to rpc client

lib/bitcoind-rpc/rpc-client.js

@@ -37,7 +37,9 @@ class RpcClient {
         return async function(...args) {
           const result = await origMethod.apply(target.client, args)
           
-          if (result.result) {
+          if (Array.isArray(result)) {
+            return result
+          } else if (result.result) {
             return result.result
           } else if (result.error) {
             throw result.error