optimize Fees.refresh()

lib/bitcoind-rpc/fees.js

@@ -53,7 +53,7 @@ class Fees {
    * @returns {Promise}
    */
   async refresh() {
-    await util.seriesCall(this.targets, async tgt => {
+    await util.parallelCall(this.targets, async tgt => {
       try {
         const level = await this.rpcClient.cmd('estimatesmartfee', tgt, this.feeType)
         this.fees[tgt] = (level.errors && level.errors.length > 0) ? 0 : Math.round(level.feerate * 1e5)
@@ -62,7 +62,6 @@ class Fees {
         this.fees[tgt] = 0
       }
     })
-
     this.block = latestBlock.height
   }